Roman Military Tactics

Last Updated on November 27, 2023 by Vladimir Vulic

Information about tactics can be derived from accounts of battles, but the very military manuals known to have existed and to have been used extensively by commanders, have not survived. Perhaps the greatest loss is the book of Sextus Julius Frontinus. But parts of his work were incorporated in the records of the historian Vegetius.

The importance of the choice of ground is pointed out.

There is an advantage of height over the enemy and if you are pitting infantry against cavalry, the rougher the ground the better. The sun should be behind you to dazzle the enemy. If there is strong wind it should blow away from you, giving advantage to your missiles and blinding the enemy with dust.

In the battle line, each man should have three feet of space, while the distance between the ranks is given as six feet.

Thus 10’000 men can be placed in a rectangle about 1’500 yards by twelve yards, and it was advised not to extend the line beyond that.

The normal arrangement was to place the infantry in the centre and the cavalry on the wings. The function of the latter was to prevent the centre from being outflanked and once the battle turned and the enemy started to retreat the cavalry moved forward and cut them down. – Horsemen were always a secondary force in ancient warfare, the main fighting being done by the infantry.

It was recommended that if your cavalry was weak it was to be stiffened with lightly armed foot soldiers.

Vegetius also stresses the need for adequate reserves. These could prevent an enemy from trying to envelope one’s own forces, or could fend off enemy cavalry attacking the rear of the infantry.

Alternatively, they could themselves move to the sides and perform an enveloping manoeuver against an opponent.

The position to be taken up by the commander was normally on the right wing.

The Tortoise

The tortoise was a essentially defensive formation by which the legionaries would hold their shields overhead, except for the front rows, thereby creating a kind of shell-like armour shielding them against missiles from the front or above.

The tortoise formation was one of the prime examples of Roman ingenuity at warfare. When deployed in such a way, the legionaries became virtually invulnerable to arrows or objects dropped from defensive walls.

The Wedge

The wedge was commonly used by attacking legionaries, – legionaries formed up in a triangle, the front ‘tip’ being one man and pointing toward the enemy, – this enabled small groups to be thrust well into the enemy and, when these formations expanded, the enemy troops were pushed into restricted positions, making hand-to-hand fighting difficult. This is where the short legionary gladius was useful, held low and used as a thrusting weapon, while the longer Celtic and Germanic swords became impossible to wield.

The wedge was an aggressive formation used to ‘crack open’ enemy lines. Relatively small groups of legionaries could form such a triangle and then drive their way into the enemy ranks. As more Roman soldiers reinforced the wedge from behind, the enemy line could be forced apart. As breaking the enemy’s formation was very often the key to winning a battle, the wedge formation was vitally important battlefield tactic of the Roman army.

The Saw

The saw was opposite tactic to the wedge. This was a detached unit, immediately behind the font line, capable of fast sideways movement down the length of the line to block any holes which might appear to develop a thrust where there might be a sign of weakness. In the case of two Roman armies fighting each other in a civil war, one might say that the ‘saw’ inevitably was the response to a ‘wedge’ by the other side.

Skirmishing Formation

The skirmishing formation was a widely spaced line up of troops, as opposed to the tighter packed battle ranks so typical of legionary tactics. It allowed for greater mobility and would have found many uses in the tactical handbooks of Roman generals.

The skirmishing formation is essentially the opposite to the closely packed line of battle used by legionaries. It is a widely spaced line. Every second man of the line has stepped forward a few paces, effectively doubling the amount of ranks. However, the gaps created by this formation are always overlapped by the next line to follow.

The roots of this formation are more than likely to be found with the velites, the lightly armed skirmishers who operated ahead of the main force in the early Roman army.

The wide spaces allow each soldier great mobility. Its possible uses were manyfold.
It would make an advance over difficult terrain much easier. It could allow for swift attacks with subsequent quick withdrawals. It would allow for any friendly units falling back to pass through the formation.
It also could be used by a victorious army sweeping over the battle field, killing all that was left in its way.

Repel Cavalry

The order to repel cavalry brought about a the following formation. The first rank would form a firm wall with their shields, only their pila protruding, forming a vicious line of glistening spearheads ahead of the wall of shields. A horse, however well trained, could hardly be brought to break through such a barrier. The second rank of the infantry would then use its spears to drive off any attackers whose horses came to a halt. This formation would no doubt prove very effective, particularly against ill-disciplined enemy cavalry.

The order to repel cavalry by Roman army officers brought about a defensive formation, in which the front rank formed a tight wall of shields with their pila protruding to form a line of spearheads ahead of the wall. Undoubtedly it would be very hard to bring a horse to break into that formation. The most likely occurrence would be that it would come to a halt of its own will ahead of the spearheads.

It was at that moment that horse and rider would be at their most vulnerable against the ranks behind the first line of infantry which would then hurl their spears at them. Given the short distance and the training legionaries received, it is likely such halted cavalry, frantically trying to turn their horses around to retreat, whilst colliding with horses following in the charge, would prove very easy targets.

If one further considers the likely possibility of archers being present, the effect of this formation could indeed be devastating.

The Orb

The orb is a defensive postition in the shape of a circle taken by a unit in desperate straits. It allows for a reasonably effective defence even if parts of an army have been divided in battle and would have required a very high level discipline by the individual soldiers.

The orb was a defensive formation in the shape of a complete circle which could be taken by a unit which had either become detached from the army’s main body and had become encircled by the enemy, or a formation which might be taken by any number of units if the greater army had fallen into disorder during a battle.

It can hence be seen as a formation representing a desperate ‘last stand’ by units of a collapsing army. But also it can be seen as a disciplined holding position by a unit which has been divided from the army’s main body in battle and which is waiting for the main force to rejoin them.

In either case, it is not a formation one would like to find oneself in, as it obviously indicates that they are surrounded by the enemy.

Naturally any officers or archers would be positioned in the centre of the orb, as can be seen in the example above.

Here are seven specific instructions by Vegetius regarding the layout before battle:

1. On level ground the force is drawn up with a centre, two wings and reserves in the rear. The wings and reserves must be strong enough to prevent any enveloping or outflanking manoeuvre.
2. An oblique battle line with the left wing held back in a defensive position while the right advances to turn the opponent’s left flank. Opposition to this move is to strengthen your left wing with cavalry and reserves, but if both sides are successful the battle front would tend to move in an anti-clockwise direction, the effect of which would vary with the nature of the ground. With this in mind it is as well to attempt to stabilize the left wing with the protection of rough or impenetrable ground, while the right wing should have unimpeded movement.
3. The same as No 2 except that the left wing is now made the stronger and attempts a turning movement and is to be tried only when it is known that the enemy’s right wing is weak.
4. Here both wings are advanced together, leaving the centre behind. This may take the enemy by surprise and leave his centre exposed and demoralized. If, however, the wings are held, it could be a very hazardous manoeuvre, since your army is now split into three separate formations and a skillful enemy could turn this to advantage.
5. The same tactic as No 4, but the centre is screened by light infantry or archers who can keep the enemy centre distracted while the wings engage.
6. This is a variation of No 2 whereby the centre and left wing are kept back while the right wing attempts a turning movement. If it is successful, the left wing, reinforced with reserves, could advance and hop to complete the enveloping movement which should compress the centre.
7. This is the use of suitable ground on either flank to protect it, as suggested in No 2

All these tactics have the same purpose , that of breaking the enemy battle line. If a flank can be turned, the the strong centre has to fight on two fronts or is forced to fight in a restricted space. Once an advantage like this has been gained it is very difficult to correct the situation. Even in the highly trained Roman Army it would have been difficult to change tactics during the course of the battle and the only units which can be successfully deployed are those in the reserves or that part of the line not yet engaged. Thus the most important decision a general had to make concerned the disposition of the troops. If a weakness could be detected in the enemy line, it was exploited by using a stranger force to oppose it. Likewise, it was necessary to disguise one’s battle line – even troops were disguised to delude the enemy. Often the very size of the army was skillfully hidden, troops packing tightly together to make it appear small, or spreading out to appear large. There were also many examples of surprise tactics made by detaching a small unit which suddenly emerged from a hidden place with much dust and noise to make the enemy believe that reinforcements had arrived.

Vegetius (Frontinus) is full of the oddest stratagems to mislead the enemy or demoralize his troops.

Once the enemy cracked, however, they were not to be surrounded, but an easy escape route left open. The reasons for this were that trapped soldiers would fight to the death but if they could get away, they would, and were exposed to the cavalry waiting on the flanks.

This important section of Vegetius closes with the tactics to be used in the case of a withdrawal in the face of the enemy. This highly difficult operation requires great skill and judgement. Both your own men and those of the enemy need to be deceived. It is suggested that your troops be informed that their retirement is to draw the enemy into a trap and the movement can be screened from the enemy with the use of cavalry across the front. Then the units are drawn off in a regular manner, but these tactics can only be employed if the troops have not yet been engaged. During a retreat units are detached and left behind to ambush the enemy if there is a hasty or incautious advance, and in this way tables can often be turned.

On a wider front, the Romans used tactics of denying their opponents the means of sustained warfare. For this they employed the tactic of vastatio. It was in effect the systematic revaging of an enemy’s territory. Crops were destroyed or carried off for Roman use, animals were taken away or simply slaughtered, people were massacred or enslaved.

The enemy’s lands were decimated, denying his army any form of support. Sometiems these tactics were also used to conduct punitive raids on barbarian tribes which had performed raids across the border.

The reasons for these tactics were simple. In the case of punitive raids they spread terror among the neighbouring tribes and acted as a deterrent to them. In the case of all-out war or the quashing rebels in occupied territories these harsh tactics denied any enemy force the support they needed to sustain a lengthy struggle.

Byzantine Tactics

By the time of the so-called Byzantine era (the surviving eastern Roman empire) true power on the battle field had long since passed into the hands of the cavalry. If there was any infantry, it was made up of archers, whose bows had longer range than the smaller bows of the horsemen.

Handbooks were published, most famously by the general and later emperor Maurice (the strategicon), the emperor Leo VI (the tactica) and Nicephorus Phocas (the updated tactica).

As with the old Roman legion, the infantry still fought at the centre, with the cavalry at the wings. But often now the lines of the infantry stood further back than the cavalry wings, creating a ‘refused’ centre. Any enemy who would try and attack the infantry would have to pass between the two wings of the cavalry.

In hilly ground or in narrow valleys where the cavalry could not be used, the infantry itself had its lighter archers at the wings, whereas its heavier fighters (scutati) were placed at the centre. The wings were positioned slightly forward, creating a kind of crescent-shaped line.

In case of an attack on the centre of the infantry the wings of archers would send a storm of arrows upon the attacker. Though in case the infantry wings themselves were attacked they could retire behing the heavier scutati.

Often though infantry was not part of the conflict at all, with commanders relying entirely on their cavalry to win the day.

It is in the tactics described for these occasions that the sophistication of Byzantine warfare becomes apparent.

The manuals indicate that a cavalry force fought in a formation looking much like this.

An example based on a force of 20 small warbands (bandae), or 4600 cavalrymen. Though in greater or lesser numbers, and with infantry or not, it is likely the Byzantine army would fight in similar array.

The main force would be the Fighting Line (ca. 1500 men) and the Supporting Line (ca. 1300 men).

The Supporting Line might have gaps in it to allow the Fighting Line to widthdraw through if necessary.

The Wings (2 x 400 men), also called the liers-in-wait tried to get behind or into the flank of the enemy in a sweeping move around the forces, far out of sight.

The Flanks (2 x 200 men) either side of the main Fighting Line were meant to prevent the enemy’s wings or flanks from circling one’s own force. Often the right Flank was also used to attack the side of the opponent’s main body. Striking from the right it drove into the left of the opponent which was harder to defend as most warriors would bear their weapons with their right arm.

At the back of the force a Third Line or Reserve (ca. 500 men) would be posted out to the sides, ready either to help defend the Flanks, to help steady any forces of the Fighting Line driven back through the Supporting Line, or to intervene in any flanking assaults on the enemy.

This leaves the general’s own escort which would most likely lie to rear of the force and would consist of about 100 men.

The Byzantine art of war was highly developed and eventually even contained specially developed tactics for specific opponents.

Leo VI’s manual, the famous tactica, provides precise instructions for dealing with various foes.

Franks and the Lombards

The Franks and the Lombards were defined as knightly heavy cavalry which, in a direct charge, could devastate an opponent and so it was advised to avoid a pitched battle against them. However, they fought with no discipline and little to no battle order at all and generally had few, if any, of their horsemen performing any reconnaissance ahead of the army. They also failed to fortify their camps at night.

The Byzantine general would hence best fight such an opponent in a series of ambushes and night attacks. If it came to battle he would pretend to flee, drawing the knights to charge his retreating army – only to run into an ambush.

The Magyars and the Patzinaks

The Magyars and Patzinaks, referred to as the Turks by the Byzantines, fought as bands of light horsemen, armed with bow, javelin and scimitar. They were accomplished in performing ambushes and used many horsemen to scout ahead of the army.

In battle they advanced in small scattered bands which would harass the frontline of the army, charging only if they discovered a weak point.

The general was advised to deploy his infantry archers in the front line. Their larger bows had greater range than that of the horsemen and could so keep them at a distance. Once the Turks, harassed by the arrows of the Byzantine archers would try and close into range of their own bows, the Byzantine heavy cavalry was to ride them down.

The Slavonic Tribes

The Slavonic Tribes, such as the Servians, Slovenes and Croatians still fought as foot soldiers. However, the craggy and mountainous terrain of the Balkans lent itself very well to ambushes by archers and spearmen from above, when an army would be hemmed in in a steep valley. Invasion into their territories was hence discouraged, though if necessary, it was recommended that extensive scouting was undertaken in order to avoid ambushes.

However, when hunting down Slavonic raiding parties or meeting an army in open field, it was pointed out that the tribesmen fought with little or no protective armour, except for round shields. Hence their infantry could easily be overpowered by a charge of the heavy cavalry.

The Saracens

The Saracens were judged as the most dangerous of all foes by Leo VI. Had they in earlier centuries been powered only by religious fanaticism, then by the time of Leo VI’s reign (AD 886-912) they had adopted some of the weaponry and tactics of the Byzantine army.

After earlier defeats beyond the mountain passes of the Taurus, the Saracens concentrated on raiding and plundering expeditions instead of seeking permanent conquest. Having forced their way through a pass, their horsemen would charge into the lands at an incredible speed.

Byzantine tactics were to immediately collect a force of cavalry from the nearest themes and to trail the invading Saracen army. Such a force might have been too small to seriously challenge the invaders, but it deterred small detachments of plunderers from breaking away from the main army.

Meanwhile the main Byzantine army was to be gathered from all around Asia Minor (Turkey) and to meet the invasion force on the battlefield.

The Saracen infantry was deemed by Leo VI to be little more than an disorganized rabble, except for the occasional Ethiopian archers who though were only lightly armed and hence could not match the Byzantine infantry.

If the Saracen cavalry was judged to be a fine force it could not match the discipline and organisation of the Byzantines. Also the Byzantine combination of horse archer and heavy cavalry proved a deadly mix to the light Saracen cavalry.

Should however, the Saracen force only be caught up with by the time it was retreating homewards laden with plunder, then the emperor Nicephorus Phocas advised in his military manual that the army’s infantry should set upon them at night from three sides, leaving open only the road back to their land. It was deemed most likely that the startled Saracens would leap to their horses and take homeward rather than defend their plunder.

Another tactic was to cut off their retreat across the passes. Byzantine infantry would reinforce the garrisons in the fortresses guarding the passes and the cavalry would pursue the invader driving them up into the valley. Like this the enemy could be helplessly pressed into a narrow valley with little to no room to manoeuver. Here they would be easy prey to the Byzantine archers.

A third tactic was to launch counter attack across the border into Saracen territory. An invading Saracen force would often turn around to defend its own borders if message of an attack reached it.