Principes Principes ( Singular : " Princeps " ) were spearmen , and later swordsmen , in the armies of the early Roman Republic . They were men in the prime of their lives who were fairly wealthy , and could afford decent equipment . They were the heavier infantry of the legion who carried large shields and wore good quality armour . Their usual position was the second battle line . They fought in quincunx formation , supported by light troops . They were eventually done away with after the Marian reforms of 107 BC . History and deployment . " Principes " appear to have been born remnants of the old second class of the army under the Etruscan kings when it was reformed by Marcus Furius Camillus . The second class stood in some of the first few ranks of a very large phalanx and were equipped in a similar manner to " principes " . They would support the heavier first class in the front ranks . It is probable that engagements with the Samnites and a crushing defeat at the hands of the Gallic warlord Brennus , who both used lots of smaller military units rather than a few very large ones , taught the Romans the importance of flexibility and the inadequacy of the phalanx on the rough , hilly ground of central Italy . Camillan system . In the early Camillan system of organisation of the 3rd and 4th centuries BC , men were sorted into classes based on wealth , the " principes " being the wealthiest after the " triarii " . " Principes " were armed with short spears , or " hastae " , up to 1 . 8 metres ( 6 ft ) long . They fought in quincunx formation , usually carrying " scuta " , large rectangular shields , and bronze helmet s , often with a number of feathers fixed onto the top to increase stature . They wore heavier armour types , the most common form being chainmail , which offered a good degree of protection without hindering movement . In this type of legion , the 900 " principes " formed 15 maniple s , military units of 60 men each . The " principes " stood in the second battle line , behind " hastati " of the first line and in front of the " triarii " in the third . In a pitched battle , the " leves " , javelin armed light infantry would form up at the front of the legion and harass the enemy with javelin fire to cover the advance of the " hastati " , light spearmen . If the " hastati " failed to break the enemy during their engagement , they would fall back and let the heavier " principes " take over . If the " principes " could not break them , they would retire behind the heavy " triarii " spearmen who would then engage the enemy in turn . The equites , cavalrymen , were used as flankers and to pursue routing enemies . The " rorarii " and " accensi " in the final battle line were some of the least dependable troops , and were used in a support role , providing mass and reinforcing wavering areas of the line . Polybian system . By the time of the Punic wars of the 2nd century BC , this form of organisation was found to be inefficient . In a new Polybian system , infantry were sorted into classes according to age and experience rather than wealth , the " principes " being older veterans with a greater degree of experience . Their equipment and role was very similar to the previous system , except they now carried swords , or " gladii " , instead of spears . Each princeps also carried 2 " pila " , heavy javelins that bent on impact to prevent them being removed from the victim or thrown back The " principes " had been increased in number to 1200 per legion , and formed 10 maniples of 120 men each . The " rorarii " and " accensi " had been done away with . " Leves " had been replaced with " velites " , who had a similar role , with forty of them being attached to each maniple in the legion . Pitched battles were conducted in a similar fashion ; the " velites " would gather at the front and fling javelins to cover the advance of the " hastati " , who had also been re - armed with swords . If the " hastati " failed to break the enemy , they would fall back on the " principes " . If the " principes " could not break them , they would retire behind the " triarii " who would then engage the enemy . This order of battle was almost always followed , the battle of the Great Plains and the battle of Zama being among the few notable exceptions . At the Great Plains , Scipio , the Roman general , formed his men up in the usual manner , but once the " hastati " had begun to engage the enemy , he used his " principes " and " triarii " as a flanking force , routing the opposing Carthaginians . At Zama , Scipio arranged his men into columns , side by side , with large lanes in between . The opposing Carthaginian elephants were drawn into these lanes where many were killed by " velites " without inflicting many casualties on the Romans . Once the surviving elephants had been routed , he formed his men into a long line with his " triarii " and " principes " in the centre and " hastati " on the flanks , ready to engage the Carthaginian infantry . Marian reforms . With the formal military reforms of Gaius Marius in 107 BC , intended to combat a shortage of manpower from wars against Jugurtha in Africa and Germanic tribes to the north , the different classes of units were done away with entirely . The wealth and age requirements were scrapped . Soldiers would join as a career , rather than as service to the city , and would all be equipped as " miles " , or soldiers , with the same , state purchased equipment . Auxiliaries , local irregular troops , would fulfill other roles , serving as archers , skirmishers and cavalry .