The Roman Legion (2nd century BC)

For the second century BC we have accounts of a slightly reorganized legion.
The hastati were still up front, carrying bronze breastplates, or the more wealthy ones among them wore chain mail coats. They now also wore purple and black feather plumes on their helmets, 18 inches in height, to increase their apparent height and appear more intimidating to the enemy. They carried a pilum, a well-crafted wooden spear with iron tip. The javelins that were carried now were short ones, only about four feet long, but with a head nine inches long, well hammered, but so fashioned that it bent on impact and could not be returned by the enemy.
The other ranks of the legion were equipped in much the same manner except that they carried a long spear, the hasta, rather than the shorter pilum.
The rorarii and accensii appear by now to have been done away with, having become velites. The velites did not form their own battle line but were divided up equally among all the maniples to compliment their numbers. It emerges that now it was the velites who were the more mobile troops who operated in the front of the army, stinging the enemy with their javelins, before retiring through the ranks of the hastati and principes

Velites

Hastati

Principes

Triarii

The divisions were now of ten maniples. The figures are a bit unclear, but what is known is that the hastati maniple consisted of 120 men.

Subdivisions of all three ranks (hastati, principes, triarii) was one of ten maniples. A maniple is defined as consisting of 160 men. (Although the hastati are supposedly had 120 per maniple. The figures are confusing. I assume that the maniple was brought its full numbers by the addition of velites. i.e. 120 hastati + 40 velites = 160 men = 1 maniple)

The soldier now used the gladius, also known as 'the Spanish sword' to the Romans, apparently due to its origin. The iron helmets had now been replaced by bronze ones again, though of thicker metal.
Each maniple was commanded by two centurions, the first centurion commanding the right, the second the left of the maniple.

The cavalry force of 300 men was divided into ten squadrons (turmae), each with three decuriones in command.

As more of the east came under Roman control, it was inevitable that an increasing number of citizens became involved in commercial enterprises and enforced army service would have been a considerable nuisance. Rome could no longer rely on a regular supply of legionaries from the simple sturdy country population. Service in Spain was particularly unpopular. The continuous series of local wars and uprisings, bad Roman leadership and heavy losses all meant hardship, possible death and little loot.
In 152 BC popular pressure in Rome was such that the time-honoured method of enlistment was modified and men were chosen by lot for a period of six years continuous service.
Another effect was an increased use of allied forces. When Scipio Aemilianus took Numantia in 133 BC Iberian auxiliaries accounted for two-thirds of his force. In the east the critical Battle of Pydna which ended the third Macedonian War was probably won by the allies, who with elephants crushed the left wing of Perseus and enabled the legionaries to split and outflank the Macedonian phalanx.
The overseas expansion also had a serious effect on the citizens of the upper classes. New opportunities of enrichment and rising corruption saw to it that competent leadership became more and more difficult to find.
The Gracchi Brothers attempted to halt the decline in the numbers recruitable for the army with land distribution and by extending the franchise to the Italian allies. But as this failed and the two brothers both were killed, the scene was set for the Social War and the arrival of Marius and Sulla.