There was an inherent similarity of Italian styles of warfare in the peninsula, which facilitated the cooperation of Romans and their Italian allies. In time, this cohesiveness allowed the development of a more sophisticated organization of Rome’s allies into larger units (alae) under Roman officers (prefects). Better incorporation and control of their allies allowed the Romans to use them very effectively in conquering and maintaining an empire.
Although the command structure used by the Romans with regard to their Italian allies is difficult to determine due to a general poor survival of evidence, there is clear evidence of greater levels of control in the third and second centuries. Before the Punic Wars, there is little indication of well-defined command structures over allied forces in Roman armies. Livy twice mentions prefects of the allies in the mid-third century, but only as part of stock phrases (Livy 8.36.5; 10.35.5; Oakley 1997? 2005, 2.749?750). That is not to say that Roman commanders were never placed over units of Italian allies (e. g. Sp. Nautius in 293, Livy 10.40.8; Frontin. Str. 2.4.1), only that there is no evidence of a regular position. With the domination of Italy by the Romans, however, a new Roman command structure developed. The exact timeline of this development is hazy, but by the Second Punic War Roman officers known as prefects of the allies (praefecti sociorum) are to be found commanding groups of Italians. These officers represent a level of command and control for Roman generals, making tactical control more effective, as well as representing the growing formalization of Roman domination of their allies. Italian commanders were apparently subordinated below these officers and appear less often in the sources. Polybius indicates that the prefects were a fully integrated part of the Roman command structure (6.26?40; Walbank 1957?1971, 1.709?723). They were appointed at the discretion of Roman generals. Twelve men were appointed to this position, six per ala (legion-like units of allies), which corresponded to the number of military tribunes in citizen legions (Ilari 1974, 128). Prefects of the allies could be used as special commanders of small detachments of allied forces, a few infantry cohorts or cavalry turmae (Livy 24.20.1; 27.41.7; 40.31.3?6; Sall. Iug. 77.4). However, in those instances where alae functioned as independent operational units similar to legions, they did so under legates as opposed to prefects.
Sometime in the third century Roman generals began organizing the allied forces drawn from other Italian communities into larger units, alae. There are some indications of groupings of allied groups in Roman armies before the Punic Wars (Livy 10.43.3; Dion. Hal. Ant. Rom. 20.1.5). However, it was not until the Second Punic War (218?201) that they are firmly attested and appear regularly thereafter. The close timing with the appearance of prefects of the allies is likely not a coincidence, as both the officers and units were closely intertwined. However, it is difficult to push this interpretation too far as sources for the early third century are quite poor and generally preserve little specific information regarding Italians in Roman armies. The alae comprised smaller cohorts drawn from allied communities and were commanded by local leaders. As a whole, the alae were similar in size to legions and could serve a similar tactical function (e. g. Livy 25.21.6; 27.1.8?13; 31.21.1?7; 35.5). In fact, in his description of the Battle of Magnesia Livy refers to the alae as legions (37.39.7; Briscoe 1981, 347). Together, the prefects and alae created a more effective system for the Romans to exploit the military potential of their allies.
The most detailed description of the Roman Republican army, including weapons, armor, command structure, castrametation, and, most relevantly here, an overview of the Italian allies as they served in Roman armies, comes from Polybius (6.19? 42). The army was divided into three lines of heavy infantry (the triplex acies) divided into age groups plus smaller numbers of cavalry and light infantry. The Italians, who had shared a common panoply prior to the Roman conquest, were organized similarly, and Livy says that at the Battle of Mt. Vesuvius in 340 the Latins fought in the same triple line (8.8; Oakley 1997?2005, 2.475?476). While no doubt anachronistic, the description is consistent with the similarities of warfare in early Italy and at the later battle at Magnesia in 189 where the Italians were organized along the same lines as the Romans (Livy 37.39.7?8). Each line was further divided into smaller subunits. For Roman infantry, these units were the maniples made up of about 160 men, three of which were grouped as a cohort. Italian infantry seem to have been organized solely in cohorts of about 500 men, or at least only cohorts are in evidence. Polybius says that the number of allied infantry coincided with the Roman infantry with three times the number of cavalry (6.27.6?9; Walbank 1957?1971, 1.709; cf. Vell. Pat. 2.15.1?2).
It seems that the two alae were typically deployed on the flanks of the two legions in a consular army (Polyb. 6.26.9; Livy 37.39.7?8). The alae, however, were not always placed on the wings, but could be deployed as needed. The Italian allies no longer formed cooperative groups, but fully formed tactical units that could undertake a variety of roles. In 181 the propraetor Q. Fulvius Flaccus in Spain deployed the left ala into an ambush position against a force of Celtiberians (Livy 40.31; cf. Frontin. Str. 2.5.8). Here not only was the ala acting completely separately from the main Roman force, but it also functioned as the core to which 6,000 Spanish auxiliaries could be attached much as the Roman legions had done for allied Italian forces. Of course, not all, or even most, Roman generals used alae so creatively, but the integration of the Italian allies was an important development in Roman warfare that created a potentially more efficient fighting force.
Beyond the alae, the allies were also grouped into a unit called the extraordinarii. Before the alae were organized, the extraordinarii were chosen by the prefects of the allies from the best men of the Italian soldiers, about 2,000 infantry and 600 cavalry (Polyb. 6.26.7?9; Walbank 1957?1971, 1.709). They were then subdivided into four cohorts of infantry and ten turmae of cavalry. While Roman armies were on the march, Polybius (6.40.8) says that the extraordinarii were either deployed in the van or the rear depending on where attacks were expected. They seem to have had no regular position in the battle-line, being deployed as needed and providing a flexible force of good soldiers (Pfeilschifter 2007, 34; Livy 40.31.3; Polyb. 10.39.1).
The Italians had become fully integrated into the Roman military system by the end of the third century. They were incorporated into the camps that Roman armies regularly constructed, although the exact details are difficult to ascertain (Polyb. 6.27? 32; Walbank 1957?1971, 1.709?716; Dobson 2008; cf. Rosenstein 2012, 93?100). The extraordinarii occupied a place of distinction near the general’s tent. Non-Italian allies camped separately. With regards to rations, Polybius (6.39.15) says that the allied infantry received the same rations as the Roman infantry, and the cavalry about onethird less than the Roman cavalry, which were given as a gift. The provision of rations can be associated with the growing disparity in relative power between the Romans and their Italian allies. In Roman eyes, it was the duty of their allies to march alongside Roman citizens across the Mediterranean, but at the same time, as with any good master, it was the duty of the Romans to care for their subordinate allies while on campaign.
The many campaigns in which the Italians participated alongside the Romans also had an impact on the complex process of cultural interchange. To be sure, units were apparently separated by ethnic groups into units and in camps (Pfeilschifter 2007; Rosenstein 2012). While fluency may have been rare, there is no reason to think that this segregation prevented passing knowledge of Latin among allied soldiers. Certainly, in those instances of discontent among soldiers, Roman citizens and Italian allies showed solidarity and cooperation (Livy 28.24.13; 40.35?36). Nevertheless, many regions in Italy show at least familiarity with Latin that must have been supported by military interaction. The Abruzzi tribes of the central Apennines were among the most common allies in Roman armies, among them the Marsi who claimed that no Roman army had ever achieved a triumph over them or without them (App. B Civ. 1.46). The earliest example of Latin used outside of Latium (in this case influenced by local Oscan), dated to the third century, comes from this area (ILLRP 7). On the other hand, the Paeligni, another Abruzzi people commonly referenced in Roman armies, show little influence from Latin in the inscriptional evidence as early as their neighbors (Bispham 2007, 5). The impact of Latin on the various languages of Italy in general reflects the same complexity of influence, adaptation, and resistance (Bispham 2007, 4?5; Benelli 2001, 7?16; Mouritsen 1998, 77?81). While other factors were at play, common military service based on centuries-old traditions of military cooperation made cultural exchange among the peoples of Italy possible.