Pilum Volley and Line Reinforcement

This page began as a review of ways in which the pilum could have been thrown. However, since the pilum was also used by soldiers in the rear ranks and in the second and third lines of the legion, the review began to cover more and more ground. The result is a long and complex html site that is the equivalent of about 25 typewritten pages. To help the reader work through the site, an outline-summary of the contents of the page is offered first. The conclusions that are reached for each section are indicated in purple.

An effort was made to be exhaustive, to consider ever possible alternative. In doing this, some ideas are presented that are not feasible. This was done to ensure the every option was considered, even those that simply need to be eliminated.


Because of the complexity of the information what follows is a summary of the points discussed and the conclusions reached about each. Following the Outline and Summary section the Body of the page gives the full details of each Scenario and describes how the conclusions were reached.

What is the range of the Pilum?

Conclusion: a pilum has to be thrown no more than 60 feet of the enemy; it cannot be thrown more than 35 feet from the front rank or less than 20 feet.

PART 1: How could all six ranks of the century in the first line throw their pila?

Scenario 1: All ranks throw their pila simultaneously from a stationary position. Not workable.

Scenario 2: All ranks throw their pila in sequence from a stationary position. Workable.

Scenario 3:All ranks throw simultaneously during the running charge. Not workable.

Scenario 4: Each rank throws its pila in sequence while running. Workable.

Scenario 5: Each rank throws in rotation before hand-to-hand fighting but not while running. Not workable.

Scenario 6: Only two ranks throw during the charge, the rest throw after hand-to-hand has begun and all ranks have closed up again. Workable.

Scenario 7: Only two ranks throw during the charge and the rest throw during later lulls. Workable.

Alternative 1: Rotate to the front, throw and charge Workable.

Alternative 2: Throw from the back, join the charge Workable.

PART 2: How might the second line have supported the first line?

Alternative 1: Spread the cohorts wider. Not likely

Alternative 2: Replace centuries on an individual basis: Not likely

Alternative 3: Use cohorts to support the line in selected places only: Possible

PART 3: How might the third line have supported the first two?

Alternative 1: Withdrawal

By Cohort: Considered unlikely

By Century: Possible

Alternative 2: Filtration

By Files: Workable.

By ranks: Workable.

Rank by rank: Not workable.

As individuals: Not workable.

Alternative method by file: Not workable.


In response to various comments and also to some discussions posted on the web, this page re-visits the question of how and when the pila of the century could have been thrown. The question has several parts to it. What is the range of the pilum? How could all six ranks of the century in the first line throw their pila? And, how could the men in the second and third lines use their pila?

What is the range of the Pilum?

A fundamental consideration is the range of the pilum. This is a somewhat complicated question. Some of the considerations are:

The distances achieved on a practice field may be quite different from those in combat, on uneven ground, amid the noise and confusion of battle.
The conditioning and practice that the Roman soldier had was quite different and may have improved his performance in ways we cannot know.
If the pilum was thrown from a full running charge it would have the added impetus of the running speed and travel further.
A pilum thrown from a standing position with only a few steps taken for the throw itself would not travel as far.
If it were thrown slightly uphill or downhill this would also change its trajectory.
The imperial pilum had an added lead weight which would have reduced distance but increased the force of impact.
Pila were not uniform and therefore would act differently once thrown.
The differences between a very good throw, an average throw and a poor throw are not known.

The estimates given in various books differ by large amounts and usually do not offer any no factual data to support them.

Earlier models used in this website used an average of 60 feet. This distance was arrived at this way.

Maximum and Average Distances: The goal would be that most of the pila thrown would hit the enemy. The entire front line of the century is presumed to throw their pila at more or less the same time and distance from the enemy. If this distance is close to the maximum distance a powerful man can throw it would mean that only a few of the pila reached the target. If they wanted to be sure that most (more than half) the pila actually reached the enemy the distance for the throw would need to be reduced to no more than (and perhaps slightly less than) the average distance the soldiers could throw.

Minimum Distances: The men in the first rank were the best troops in the unit, the initial clash was the single most important moment in the entire battle for it could, and apparently often did, decide the course of the contest. The Romans would certainly not adopt a system that endangered their front line troops at the moment of combat. Therefore, when considering how far a soldier in the rear ranks might throw an important consideration is that the pilum safely clear the heads of those in the front ranks.

What is important is that all throws clear the ranks in front, not just most or some. The real question is how bad would a bad throw have been. And, of course, there is no way to know that. Consider a poor throw of 50 feet. The illustration below shows throws of 60 feet (average) and 50 feet (poor).

What needs to be observed is that if the 50 foot throw were to hit an enemy soldier the butt of the pila is some 6 to 8 feet closer. To provide 2 feet of clearance between the butt of the pila and the man in the front rank, the soldier making the 50 foot throw cannot be any further than 35 feet behind his own first rank.

On the other hand, the pilum cannot be thrown too close to the enemy either. This illustration shows why.A short throw, in this case, 28'6", that has to be lofted up over the heads of men in front cannot be a hard throw. The trajectory calculator (see Appendix C) estimates that a pilum thrown in this manner would have an initial velocity of just 22 miles an hour, about the speed of a softly thrown underhand softball. The pilum would be in the air less about 9/10 of a second. During that time, and given the angle of its release, it would not have time to rotate. It would land flat instead of point first.

The arc in the drawing is correct, the angles of the pilum at various points in the trajectory are not accurate, they are for purposes of illustrating the point only. The trajectory calculator does not permit the calculation of the rotational speed of the pilum. The amount of rotation would also depend on the weight distribution of the weapon. The imperial pilum, with its lead weight at the front, would rotate faster.

How close is too close? This might be a matter for experimentation by re-enactors with various types of pila. In general, however, a lofted throw of less than 30 feet would seem to be too close, lacking in impetus, and possibly landing flat instead of point down. Without further information, the model will assume that 20 feet is the minimum.

These two illustrations give three critical data points needed for the model: (1) a pilum volley has to be thrown no more than 60 feet of the enemy; (2) it cannot be thrown from more than 35 feet behind the front rank and (3) it cannot be effectively thrown at distances of less than 20 feet.

PART 1: How could all six ranks of the century in the first line throw their pila?

Several scenarios will be illustrated. To make the drawings workable, symbols will be used instead of more realistic line drawings. The drawing below shows the line drawings and their related symbols.

From left to right the figures are: pilum-ready, pilum-marching, pilum-charging. pilum-throwing, sword-charging, sword-fighting, sword-ready, sword-replaced

Pilum-at-the-ready: standing still with pilum at the ready.

Pilum-marching: moving toward the enemy at a march pace prior to the running charge.

Pilum-charging: the running charge with the pilum ready for the throw.

Pilum-throwing: the moment of release, this symbol is shaded a solid color to help distinguish it from the previous symbol.

Sword-charging: the running charge with sword in hand.

Sword-fighting: the active hand-to-hand fighting phase.

Sword-ready: standing sword in hand, prepared to fight.

Sword-replaced: this symbol represents the soldier who has withdrawn from the front line after a period of hand to hand fighting and is considered exhausted and no longer ready to fight. Given sufficient time, this soldiers status could return to the Sword-ready position.

For the development of some models a century of 6 ranks and 10 files will be used as generally representative of a somewhat understrength century. For the sake of simplicity each rank will be considered a single unit and no distinction will be made between individual in the rank.

Seven scenarios will be discussed:

1. All ranks throw their pila simultaneously from a stationary position
2. All ranks throw their pila in sequence from a stationary position
3. All ranks throw simultaneously during the running charge.
4. Each rank throws its pila in sequence while running.
5. Each rank throws in rotation before hand-to-hand fighting but not while running.
6. Only two ranks throw during the charge, the rest throw after hand-to-hand has begun and all ranks have closed up again.
7. Only two ranks throw during the charge and the rest throw during later lulls.

Scenario 1: All ranks throw their pila simultaneously from a stationary position

This Scenario supposes that all six ranks hold their initial positions, await the charge of the enemy (green) and then all six ranks throw their pila simultaneously. This is illustrated on the right.

The illustration shows three frames. In the first the century is lined up in its normal order, files on 3 foot intervals, ranks on 4 foot intervals. To make room for throwing their pila the ranks are spread out to 7 feet in the second frame of the illustration. The third frame shows them in the act of throwing. The enemy is shown as the green army in the third frame.

There are two purple lines in the third frame. The first is at the edge of the green century. It represents the line 60 feet from the back most rank of the blue army. If the blue century is to throw simultaneously it cannot throw until the green army reaches this mark or the pila of the last ranks will fall short.

The other purple line is just behind the first rank of the blue army. It represents the danger zone, 35 feet from the back rank. The front rank is in the danger zone.

There are only 17 feet between the first ranks of the two armies, just a few steps for the charging green army which could cross the distance in a second or so, less time than it would take for the blue century to recover from the throw and draw its swords.

The effect of the dense volley of pila is not included in these estimates. However, overall casualty statistics would argue against too devastating an effect.

Because of the extremely short distance between the armies and the fact that the first rank of the blue century is in the danger zone this does not seem like a feasible solution.

This is not considered a workable scenario and is presented only by way of eliminating it.

Scenario 2: All ranks throw their pila in sequence from a stationary position

This scenario is more feasible. It is similar to the Scenario 1 except that the six ranks take turns throwing. This makes a big difference because the extra space needed for throwing is only required for one rank at a time. This allows the entire formation to be more compact and provides the necessary clearances.

This illustration has 7 frames in it. The blue army is stationary and each rank takes its turn stepping forward and throwing its pila. Meanwhile the green army is charging and throwing on the run (its method of throwing its pila is presented as Scenario 4 below. Note the change in symbols from triangle (armed with a pilum) to circle (armed with a sword). The horizontal orange lines are 30 feet apart, two lines represent the average pilum range, one interval is roughly the danger zone.

This scenario is considered feasible and, in fact, appears to have been used. This scenario reflects the defensive tactic described by Alexander Zhmodikov. Pompey's forces received the charge of Caesar's men at Pharsalus while holding their positions. Caesar describes defensive battles in which his men threw missiles from their defensive works. The battle of Ilerda featured several cohorts in essentially stationary positions throwing pila at each other for a matter of hours.

Scenario 3:All ranks throw simultaneously during the running charge.

The position would be essentially the same as Scenario 1 except that all of the ranks would be running while they try to throw their pila. All of the same problems would exist as were outlined for Scenario 1. In addition, since the men are now running, the first rank would collide with the enemy in about 3 steps, well before they had time to recover from the throwing motion.

This scenario is not considered feasible and is presented only to eliminate it.

Scenario 4: Each rank throws its pila in sequence while running.

This is the method that was presented in the original webpages in the section Model of the Charge.

The illustration has 13 frames showing the entire sequence from the start of the charge through to actual contact with the enemy.

Frame 1 shows the two armies about 120 feet apart. The three orange lines divide the field into 30 foot slices. In frame 2 the first ranks starts to run, followed by the second rank in frame 3. By allowing each rank to start its run before the one behind it space is created between the ranks to make room for them to throw their pila.
In the 6th frame the two sides are within 60 feet of each other and the first rank throws its pila. The first ranks of the two armies would collide in frame 10, while the 5th rank is throwing its pila. All six ranks do not fully close up until the 13th frame.

The following details shows the six frames in which the ranks throw. The first rank reaches the center line -- the place where the two armies would meet -- in the second frame from the right. In that frame the 5th rank is throwing from a distance of 35 feet back, just at the edge of the safety margin.

The symbols with circles indicate that the rank has thrown its pila and is now armed with swords.

This illustration, taken from The Model of the Charge page, shows how, by taking 2 marching steps after the man in front starts his run, the distance between successive ranks can be increased to 9 feet to allow room for throwing the pila. The advantage to this is its simplicity. When he sees the man in front of him start to run each soldier simply takes two more walking steps before he himself starts to run.

Overall this scenario is feasible. The distances work out. Each successive rank throws within 60 feet of the enemy and at the same time its own front rank is never more than 35 feet away, although this is cut close for the last two ranks.

But there are problems with it as well. While the scenario works for six ranks, it would not work for a deeper formation of 8 or 10 ranks. Any rank beyond the sixth would be too far back to safely clear the front rank.

The other problem is that the scenario is a bit complicated. Each rank has to start of a step later than the one in front. It then has to wait its turn to throw and be sure it is within 60 feet of the enemy and also within 35 feet of its own first rank. This would be doable in theory, in practice it might be difficult to accomplish given the excitement of battle. Ranks could easily step out too soon, not leaving sufficient space for the throw. Worse, they could throw too soon, while they are too far back, and endanger their own men in front. It is tempting to simply say Roman training would have avoided these problems but that is merely an assumption and may not fully take into account the difference between drill and battle.

Scenario 5: Each rank throws in rotation before hand-to-hand fighting but not while running.

This scenario has 13 frames. Frames 6 through 11 show the six ranks throwing their pila in turn. After each rank has thrown it steps aside and then to the rear to allow a new rank to move to the front. Eventually the first rank becomes the sixth rank. Once the sixth rank has thrown their pila the entire unit, now armed with swords, charges.

The positions of the green army are shown as if they were charging using the method described in Scenario 4. The critical elements are the times and distances. In each frame the green army is within range of the rank throwing. As for time, the critical time is in the last frame, from the throw in frame 11 to the collision in frame 13. In Frame 11 the two sides are only 18 feet apart. It would take the green army less than two seconds to close this gap, possibly not long enough for the blue army rank to recover from the throwing motion, draw their swords and brace for impact.

The enlargement of frames 8 and 9 below show how the ranks that have already thrown (now represented as circles) filter to the rear as the remaining ranks move forward for their throw.

The frames above are roughly one second apart in time. The process of throwing, moving aside and allowing the next rank to throw would almost certainly take longer than two seconds. Therefore the illustration below may be more accurate. The throws of the blue army are now shown two seconds apart. However this does not allow enough time for all six ranks to throw before the green army is upon them.

The plan in Scenario 5 does not seem like a feasible solution.

Scenario 6: Only two ranks throw during the charge, the rest throw after hand-to-hand has begun and all ranks have closed up again.

There are 15 frames in this illustration. The first two ranks throw during the initial charge (frames 6 and 7). The other ranks hold their pila until the entire unit has closed and the first ranks are actually in contact with the enemy. They then throw their pila one rank at a time (frames 11-14)

The enlargement below shows all of the throws (frames 6 through 14)

The advantages of this scenario are that only two ranks have to make the difficult throw during the running charge. There is virtually no danger of injury to men in front of them, as there was in Scenario 4. The last four ranks throw only when they have nicely closed up the distance and can more or less take their time about it.

The disadvantage may be that very closeness. When the third rank throws (frame 11) it is only 26 feet to the last rank of the green army. This may be too close. A pilum thrown with maximum force and at an angle sufficient to clear the plumes of the men in front might well go right over the heads of the enemy soldiers. Of course, the enemy formation might not be as small or as tightly bunched as the one illustrated.

The overall scenario seems plausible but does have the difficulty of the pilum throws being somewhat short and, consequently, of less than maximum force.

Scenario 7: Only two ranks throw during the charge and the rest throw during later lulls.

This scenario has 12 frames. Only the first two ranks are shown throwing their pila (frames 6 and 7). The other ranks hold theirs for later use, illustrated below.

The enlargement below shows the throws by the first two ranks and how the rest of the century retains their pila. The circles represent soldiers armed with swords, the triangles indicate that they still have their pila.

This scenario supposes that the two sides fight for a relatively short time and then back away from each other as the fighters become exhausted. The other ranks throw their pila during the lulls in the fighting. The next two sets of illustrations show two ways in which that could have been done.

Alternative 1: Rotate to the front, throw and charge

The above illustration shows the position after the two armies have backed away from each other after the initial phase of hand-to-hand combat. The first two ranks of the blue army are now shown as diamonds, indicating that these ranks have been engaged in energetic fighting and are exhausted. In the second frame they step aside to let the fresh third rank move to the front. The third rank throws its pila and then mounts a fresh charge against the enemy, followed by the original first two ranks who will support them. The remaining three ranks, still armed with pila, follow the formation forward but would have to get rid of their pila before actually participating in the hand-to-hand fighting.

In this system, the two sides would repeatedly engage in brief hand-to-hand fighting, followed by lulls and separation. The sequence of mounting a new charge by moving a fresh rank to the front, throwing their pila and charging with swords could be repeated for each of the ranks.

Alternative 2: Throw from the back, join the charge

In this alternative the ranks do not exchange places. The rear ranks throw their pila, but from their original locations. The illustration shows ranks three and four throwing their pila. Then the century charges, this time with four ranks of swordsmen and two ranks of pila-armed men. The illustration shows two ranks throwing, it could just as well show 1 or all 4 ranks throwing.

The great advantage of this alternative over the one above is that it keeps the best fighters, the original first rankers, in the forefront.

The great disadvantage is exactly the same. It does not provide a fresh rank for the renewed attack.

But this gets back into a discussion of just how soldiers were replaced.

PART 2: How might the second line have supported the first line?

This section is closely related to the general question of line replacement.

Line replacement as such is a term that should probably be limited to discussions of the manipular legion. In that context it referred to the complete and almost simultaneous replacement of one line with another. The cohort legion of the late republic and empire probably did not engage in anything like a total line replacement.

However there is a certain parallel issue in the cohort legion. The most common legion formation appears to have been the triplex acies. Current discussion revolves around the position and function of the second line. In one view the second line existed as a maneuvering formation and by the time the battle was actually joined it had joined up with the first to form an unbroken front of 7 cohorts. The other view, more traditional, considers the second line a reserve line but one that probably worked very closely with the first line to actively support it throughout the battle.

In both views the third line is considered to be more of a strategic reserve.

The illustration below shows the two formations.

In either case there would come a time when the line(s) in back would be called upon to support or reinforce the front line. This is sometimes credited with being the turning point of the battle, when the fresh men enter the fray.

There are only about three different ways this could be done.

Alternative 1: Spread the cohorts wider.

This illustration shows the cohorts of the third line (on the left) and the second line (on the right) spread out laterally to cover the entire front.

On the left the front line of the legion is 7 cohorts wide. On the right it is 4 wide.

While there probably was no single uniform standard, a typical century might be 10 files wide by 6 or 8 deep (shallower if the legion were understrength). Using 6 as an example, the cohort would be 60 files wide by 6 deep. The 7 cohort legion is, then, 420 files wide. The 4 cohort legion is 240 files wide.

Both formations are supported lines of 3 cohorts of 360 men each, for a total of 1080 men.

In the 7 cohort legion on the left they are shown spread thin to cover the 420 files of the front line. 1080 divided by 420 gives a depth of 2.57 men per file. That is, the cohorts of the third line would be 140 files wide but less than three men deep.

In the 4 cohort front on the right there are 240 files in the front line, covered by 1080 men in the second line. In this case the second line cohorts have to be 80 files wide and 4.5 men deep.

PRO: If the legion is viewed as a long line of men without regard to the divisions by century and cohort then this solution may be feasible. It has the merit of simplicity. It simply spreads all of the supporting or reinforcing troops equally along the front to be covered.

CON: The divisions into century and cohort do not seem minor. It does appear that cohorts acted as cohesive units. Certainly the standards of the century were important for the organization of the fighting unit. Men were trained to organize themselves around the standards, to follow them, to assemble around them.

If the centuries and cohorts of the supporting lines were spread wider than those in the front lines it is difficult to see how they could have been used to replace them without destroying unit cohesion. The illustration on the right shows how this might have looked for the 4 cohort legion. The centuries illustrated are those on the far right of both the first and second lines, this time the second line centuries are shown right behind those of the first line.

The century with the X through it illustrates the problem particularly well. How could this century be used to reinforce the two centuries in front of it without loosing its cohesion? Clearly the men of the X'd century could not be assigned to the two centuries as they are without destroying its identity.

The problem is much worse when the 7 cohort front is considered. In that case each supporting century spans 2 1/4 front line centuries.

The other alternative for using these spread-out supporting centuries would be to have them fully replace the first line centuries -- along the lines of the manipular line relief. In this scheme the front line centuries or cohorts would physically withdraw from the line, leaving an open path for the replacing centuries to move forward into the line.

Even were this possible it would not be a very credible maneuver. In the 4 front formation the army would be replacing 4 cohorts with three, in the 7 cohort front formation it would be 7 replaced by 3. In neither case would one consider it a stronger formation after the replacement.

The conclusion is that this system of using the reinforcing lines does not seem to be very credible.

Alternative 2: Replace centuries on an individual basis:

This illustration shows the cohorts of the supporting line broken into individual centuries with each century supporting or reinforcing a single century of the forward line. This is not a credible solution and is shown only to eliminate it from consideration. The single most important problem is that it completely breaks down the cohesion of the cohort. We do not find Caesar, for example, talking about centuries as tactical units, only cohorts. A model that destroys the integrity of the cohort cannot be considered credible.

Alternative 3: Use cohorts to support the line in selected places only:

The only other way that seems possible is for the cohorts to retain their standard formations (preserve the numbers of ranks and files) and to reinforce the front line at only selective places -- where the need is the greatest.

This solution seems very much in keeping with the tactical reserve role of the third line. Cohorts are sent from this line to whatever part of the battlefield is in need of them.

This solution seems somewhat less satisfying when applied to the second line. The 4 cohort front formation supposes that the second line of cohorts works closely with the first line so that as the battle progresses both lines become fully involved in the fighting as a matter of course. This would seem to imply that the second line should support the first more or less along its full front and not just in selected places.


Of the three alternatives the third seems the most likely, although it is less than fully satisfying when applied to the 4 cohort front formation.

PART 3: How might the third line have supported the first two?

The question now moves to the next phase in the process. Assuming that at some point the cohorts of the third line are sent to support or reinforce the first line, just how might it have been done. This section is built on Alternative 3 above, in which the supporting cohorts retain their formation and replace front line units on a one-for-one basis. That is, one century of front line troops are replaced by an equal sized century of supporting troops.

The specific question being considered is just how these second or third line supporting troops could have used their pila. Just how did they get close enough and find enough room to put their pila to effective use?

There are two different types of solutions.

Alternative 1: Withdrawal

In one way the easiest solution is to propose that the front line unit, be it century or cohort, simply move back and out of the way, leaving a clear path for the supporting unit to enter the battle.

By Cohort:

This illustration shows three frames of the process of replacing one cohort (red) with another (green). In the second frame the red cohort has withdrawn from the line and moved to the side. The illustration shows a blue cohort in the second line behind the new position of the red cohort, as would be the case when several replacement cohorts were working together. Even if the other supporting cohort were not there, the red cohort would still have to move away to the side.

When the red cohort has cleared the field the green cohort could attack the enemy (not shown) in much the same way as the initial charge was launched. They could mount a running charge, throw their pila at about 60 feet and attack with swords.

This is the easiest way for the second or third line cohorts to have entered the fighting.

The difficulty is with the maneuver required for the withdrawal of the red cohort. Each man would have to move backward about 44 feet and sideways about 240 feet. Even if the maneuver were executed during a lull in the fighting in which the two sides were some distance apart it would be difficult. The entire cohort could hardly just turn its back on the enemy and march to the rear. Backing up a formation 40 feet wide and over 200 feet wide would be nearly impossible, as Delbruck noted for even the smaller 120 man maniple.

By Century:

Where it seems almost impossible to imagine an entire cohort being replaced at one time, it is somewhat easier to imagine the century being replaced.

The three frames below show the same cohorts as above, this time with the unit replacement being done one century at a time.

The men of the century still have to retreat 44 feet but this time they only have to move about 45 feet to one side. Furthermore, since only 1/6th of the cohort is in motion at any one time the entire formation has much greater stability. Even if there were a disruption to the maneuver of the century -- if, for example, some men tripped and the ranks and files were confused -- the resulting damage to the integrity of the cohort formation would be minimal.

Of the two methods, replacement by centuries seems more feasible than replacement by cohorts.

If wholesale replacement of units was not done, the alternative would seem to be some method of infiltrating fresh troops to the front. That alternative is explored below.

Alternative 2: Filtration
By Files:

The first filtration scenario is by files. That is, each file of the leading century pulls out and is replaced in turn. The second frame shows the right hand file turned to face backward and running to the rear of the formation. In frame 3 the retreating file has run clear and the replacement file is moving forward. Note that the retreating symbol is the diamond indicating an exhausted soldier armed with a sword, the replacement symbol is a triangle indicating a fresh soldier still carrying his pilum. In the fourth frame the replacement of the first file is complete and the second file has begun its retreat.

It is important to attach some time estimate to this maneuver. The retreating men must turn around and run about 25 feet to clear the file. At the charging running pace they would cover just over 8 feet per second. In three seconds the file should be able to run clear. The replacement soldiers start about 20 feet back so have to run about 45 feet, taking about 6 seconds. Add one second for reaction times and the replacement of a single file should take about 10 seconds. Ten files could be replaced in about 2 minutes.

The critical factor, however, is not so much the total time as the time that the formation is disrupted and, therefore, vulnerable. Since only a single file at a time is in motion the disruption is limited to about 10 seconds. This is not enough time for an effective attack against the formation.

By files:

The other method of replacement by filtering men into the front would be by rank. This is quite similar to the method used in Scenario 5 above in which each front rank stepped to the side and back, allowing the rank behind it to move forward. To use this system for the replacement of an entire century would merely require an extension of the process to include the fresh ranks of the new century in the back. This is illustrated below.

The time estimate for completing this maneuver is only one minute. This allows 20 seconds for the replacement rank to move forward the 30 feet or so to the front. That is only two short steps of 18 inches per second, a very slow advancing pace; one that should be possible even in the restricted space available. It allows twice that long, 40 seconds, for the retreating century to back out of the formation. This is only 1 short step of about the length of one's own foot every second, a very slow and cautious pace. Even stepping backward a soldier might do this without too much difficulty.

Even if the maneuver took twice or three times as long as estimated, the entire unit would not be vulnerable for a very long period of time. While the replacing unit is working its way through the ranks the front line remains undisturbed. As soon as the retreating century has withdrawn as little as 6 feet the integrity of the front lines are again restored. The actual length of time that the front rank would be disrupted is probably less than 15 seconds.

The great difficulty with this system is that it requires the two centuries to squeeze past each other within the standard 3 foot space provided for each file. The nominal depth of a man is only 12 to 15 inches so that, turned sideways, two men should be able to pass within a 3 foot area. The presence of armor, shields, pila and drawn swords would make it much more difficult. Would it be possible? On paper it seems so. In reality, this may be another question best left for reenactors to experiment with.

In either of the two plans offered above, once the replacement has been completed the new front century could employ its pila in one of the various scenarios already illustrated.

Rank by rank:

This method would have each replacement rank move forward singly rather than all six at one time. The method would be precisely the same as described above in the filtering by ranks section except that only one rank at a time would be involved. This would make the entire process somewhat easier in that the whole century would be able to move and make room more easily. This method is not illustrated since it is so similar to the one above.

The result of this type of replacement would be to have a new front rank armed with pila. It would be supported by the former front rank, not by fresh troops from its own century. This is a disadvantage to this plan since it breaks up the unity of the replacing century and does not provide the best level of support to the fighting front rank.

It is not considered a particularly viable option.

As individuals:

This method of replacement is essentially the same as the one above, by ranks, with the exception that it supposes that each individual moves forward in response to the needs of that particular file. Replacement is individual by individual. Whole ranks to not move at the same time. This would be the easiest filtration method since only one person at a time is moving forward or backward inside the unit. But it is also not particularly effective at brining a solid block of fresh men to the front to make a new attack. There is no shock value to one man coming to the front and throwing his lone pilum.

This is not considered a good option.

Alternative method by file:

There is an alternative replacement by file method that can be considered. Instead of each replacing file taking up the same position as the retreating file it could be done another way. The retreating files could leave from, say, the right side of the formation with the remaining files shifting to their right leaving an open file on the left for the replacing files to enter. As each file left the remaining files would shift to the right making room for another file to fill on the left.

This is a scenario that was once proposed in a discussion group.

It is not considered viable since it would involve too much lateral movement and would not offer a significant advantage of other more simple solutions.

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© 2003, Gary Brueggeman. All rights reserved world wide. No part of this work may be reproduced in part or whole, in any form or by any means, without permission from the author.