Marching to the Battlefield

Parallel Columns

The typical battlefield was chosen to provide open ground for maneuver. In most cases the army could move from the assembly point to the battlefield in as many parallel columns as it wished. One would like to imagine an orderly march forward in nice straight lines. However, if there were obstacles (trees, hills, marshy ground, ravines or just rock outcroppings), the columns would have to work around them. In some cases we know that the army actually forded rivers on the way to the battlefield. By marching in as many parallel columns as possible the army gets to the battlefield in the most efficient manner while still being able to maneuver through rough ground.

From the point of assembly to the battlefield is 1.16 miles. The army could cover this distance in under 30 minutes. As well conditioned as the Roman soldier was, he could probably have done it in half that time if pressed.

The illustration on the right shows in a very general fashion how the army might have been able to move from its assembly point at the bottom, through broken terrain to the final battle position at the top. The wavy lines indicate that each column has to find its own path through the obstacles. An army trying to march in a broad formation cannot do this, one in narrow columns can.

From Column to Century

What remains is to examine how the columns-of-two's converted themselves into a battle array.

As the scenario has been worked out, the columns-of-two's retain their internal structure from the time they are form up at the tent site to the time they deploy into the final battle formation. The illustration below shows the century lined up in front of its tents ready to begin the march. As has been noted, many, perhaps most, of the contubernia would have had some men missing or on detached duty. This would leave holes in the formation, as can be seen in the illustration. As soon as the column begins to move out, however, the men move forward to fill in the gaps.

The next illustration shows the column in its stationary form and the same column in a marching form, with all of the gaps filled. The red lines group the men by contubernia. With even a few random gaps in the formation the contubernia groups become misaligned.

At one point it was thought that the files of the century could be comprised of one contubernium each. Even a quick look at the illustration will show that there is no easy or direct way a marching column could convert itself into a rank and file formation and keep all of the contubernia together as files. It would not be impossible, but it would take extra steps, slow the process down, and create potential bottlenecks. And, in the long run, if the ranks and files are too uneven, men would have to be moved from one file to another to fill in, destroying the system. Therefore the notion of keeping contubernia together has been abandoned.

Fill by Files

The easiest and most direct way to get from a column-of-two's to a rank and file formation is to fill in by files. This process is illustrated in the 8 frames below, running from left to right.

Frame 1: The column is almost at the assembly point. The centurion leads the column to the assigned mark*. The signifer, cornicen and optio have dropped out of the line to the left. After counting out the right number of files, the optio holds up the remainder of the column to fill in the next two files.

*The mark: There would have to be some mark on the field to guide the column -- a flag, stake in the ground, or even a person. If the army deployed in sequence from right to left then each unit could locate its place based on the one to its right. But this would take a very long time. In the scenario worked out here, the army moves and deploys in many parallel columns. If it is to do this, then each column, or at least every few columns, has to have some pre-determined mark to aim at so that the entire formation has the proper spacing. The commander may even have sent his surveyors out the day before to measure and mark the battlefield and the assembly points. If this were so, then the armies could learn something of the enemy's intended dispositions by carefully observing the activities of these surveyors.

Frame 2-8: The process of filling in the files continues. The centurion at the front guides the columns into the correct location and ensures that the first file is aligned with the centuries on either side of it. The optio controls the movements of the column. In the final frame, the ranks and files are dressed, the centurion is in place and the unit is ready for battle.

Problem: While filling by files is direct and simple it has one major drawback. Men end up in the front rank by chance, not design. It would seem more likely that the Romans carefully selected the front rankers to ensure that the best and bravest were there. It is difficult to see how this could be done using a fill by file system. Is this a problem? For now this is an open question.

Fill by Ranks

It would be possible for the column to turn as it gets to the assembly area so that it fills in the formation by ranks. This method of filling in the formation partially solves the problem noted above. If the best fighters are at the front of the right hand column then they will end up in the front rank. However, this is only a partial solution. Given the way this model is supposed to have worked, the column is formed as the men muster in front of their tents. The only way the best fighters could be placed in the front of the column would be to group them all together in the first and second tents of the century. And then they would have to be sure to line up on the right, not the left, side of the column.

It is not a perfect solution, but it could have worked.

The process is not significantly more complicated than the fill by file method and seems like it would be quite feasible.

Adjusting the Gaps

Even in the final battlefield formation the centuries would wish to have some small gaps between them for maneuverability. Delbruck repeatedly makes this point. Just how big those gaps would need to be is not known. The models have used six feet as a minimal gap.

Keeping in mind that there are multiple parallel columns forming up as centuries, as they line begin to fill in there would inevitably be some places where the space between adjacent centuries is either too narrow or too wide. A method of adjusting for this is shown below.

There are two illustrations below, side by side. In each illustration there are two frames -- a "before" on the left and an "after" on the right. The desired gap of six feet is shown by the two orange lines.

On the left, in frame 1, the gap is to small for the final two files so in frame 2 the optio sends one file forward and diverts the other one to form a 7th rank along the back of the formation. The formation ends up 9 files wide by 7 ranks deep.

On the right, in frame 1 the gap is too wide after all of the 10 files have been filled. In frame 2 The optio pulls one man off the back of the last file and diverts the final four men in the column to fill in an additional file. The formation ends up 11 files wide but only 5 ranks deep on the left.

The above scenarios show how the century would adjust its front and the gap between it and the one next to it while still in the process of forming up. Another possibility (illustrated below) is that the century would fully form up into its standard number of ranks and files (frame 1) and then divert men into the open file on the left (frame 2). While this would work in cases where the gap is too wide, it would not work when the gap is too narrow for the century might not even have room to form properly in the first place. Therefore, it is more likely that the optio made the adjustment as the column was filling in the ranks or files, as shown above.

The final piece to the deployment of the army is to consider just how the battle formation differed from the illustrations usually shown in books.

Links to the five parts of the Deployment section:
Deploying the Army: Planning
Deploying the Army: Exiting the Camp
Deploying the Army: Assembling the Units
Deploying the Army: Marching to the Battlefield
Deploying the Army: Forming in Battle Formation

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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.