The following is their manner of breaking up camp. Immediately upon the signal being given they take down the tents and every one packs up. No tent, however, may be either taken down or set up before those of the tribunes and consul. On the second signal they load the pack animals, and on the third the leaders of the column must advance and set the whole camp in movement. They usually place the extraordinarii at the head of the column. Next comes the right wing of the allies and behind them their pack animals. The first Roman legion marches next with its baggage behind it and it is followed by the second legion, which has behind it both its own pack animals and also the baggage of the allies who bring up the rear; for the left wing of the allies forms the extreme rear of the column on the march. The cavalry sometimes marches in the rear of the respective bodies to which it belongs and sometimes on the flanks of the pack train, keeping the animals together and affording them protection.
Roman Army – Trajan’s Column
When an attack is expected from the rear, the same order is maintained, but the allied extraordinarii not any other portion of the allies, march in the rear instead of the van. Of the two legions and wings each takes the front or rear position on alternate days, so that by this change of order all may equally share the advantage of a fresh water supply and fresh foraging ground.
They have also another kind of marching order at times of danger when they have open ground enough. For in this case the hastati, principes, and triarii form three parallel columns, the pack trains of the leading maniples being placed in front of all, those of the second maniples behind the leading maniples, those of the third behind the second and so on, with the baggage trains always interposed between the bodies of troops. With this order of march when the column is threatened, they face now to the left now to the right, and getting clear of the baggage confront the enemy from whatever side he appears. So that very rapidly, and by one movement the infantry is placed in order of battle (except perhaps that the hastati may have to wheel round the others), and the crowd of baggage animals and their attendants are in their proper place in the battle, being covered by the line of troops.
When the army on the march is near the place of encampment, one of the tribunes and those centurions who are specially charged with this duty go on in advance, and after surveying the whole ground on which the camp is to be formed, first of all determine from the considerations I mentioned above where the consul’s tent should be placed and on which front of the space round this tent the legions should encamp. When they have decided on this, they measure out first the area of the praetorium, next the straight line along which the tents of the tribunes are erected and next the line parallel to this, starting from which the troops form their encampment. In the same way they draw lines on the other side of the praetorium. All this is done in a very short time, as the marking out is a quite easy matter, all the distances being fixed and familiar; and they now plant flags, one on the spot intended for the consul’s tent, another on that side of it they have chosen for the camp, a third in the middle of the line on which the tribune’s tents will stand, and a fourth on the other parallel line along which the legions will encamp. These latter flags are crimson, but the consul’s is white. On the ground on the other side of the praetorium they plant either simple spears or flags of other colours. After this they go on to lay out the streets and plant spears in each street. Consequently it is obvious that when the legions march up and get a good view of the site for the camp, all the parts of it are known at once to everyone, as they have only to reckon from the position of the consul’s flag. So that, as everyone knows exactly in which street and in what part of the street his tent will be, since all invariably occupy the same place in the camp, the encamping somewhat resembles the return of an army to its native city. For then they break up at the gate and everyone goes straight on from there and reaches his own house without fail, as he knows both the quarter and the exact spot where his residence is situated. It is very much the same thing in a Roman camp.
The Romans by thus studying convenience in this matter pursue, it seems to me, a course diametrically opposite to that usual among the Greeks. The Greeks in encamping think it of primary importance to adapt the camp to the natural advantages of the ground, first because they shirk the labour of entrenching, and next because they think artificial defences are not equal in value to the fortifications which nature provides unaided on the spot. So that as regards the plan of the camp as a whole they are obliged to adopt all kinds of shapes to suit the nature of the ground, and they often have to shift the parts of the army to unsuitable situations, the consequence being that everyone is quite uncertain whereabouts in the camp his own place or the place of his corps is. The Romans on the contrary prefer to submit to the fatigue of entrenching and other defensive work for the sake of the convenience of having a single type of camp which never varies and is familiar to all.
(Source: Polybius, The Histories, Vol.IIΙ, Book VI, Loeb Classical Library)
Research-Selection for NovoScriptorium: Anastasius Philoponus