Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
The old Doric phalanx had been wholly adapted to close combat with the sword and especially with the spear, and only an accessory and subordinate position in the order of battle was assigned to missile weapons. In the manipular legion the thrusting-lance was confined to the third division, and instead of it the first two were furnished with a new and peculiar Italian missile weapon, the -pilum- a square or round piece of wood, four and a half feet long, with a triangular or quadrangular iron point--which had been originally perhaps invented for the defence of the ramparts of the camp, but was soon transferred from the rear to the front ranks, and was hurled by the advancing line into the ranks of the enemy at a distance of from ten to twenty paces.
At the same time the sword acquired far greater importance than the short knife of the phalangite could ever have had; for the volley of javelins was intended in the first instance merely to prepare the way for an attack sword in hand. While, moreover, the phalanx had, as if it were a single mighty lance, to be hurled at once upon the enemy, in the new Italian legion the smaller units, which existed also in the phalanx system but were in the order of battle firmly and indissolubly united, were tactically separated from each other.
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Reference address : https://www.ellopos.net/elpenor/rome/2-08-law-religion-army-economy-nationality.asp?pg=18