Roman amphibious doctrine is described as landing auxiliaries and light infantry first, followed by heavier troops. In the Republican sequence, hastati and principes preceded the triarii, the veteran troops normally held until last. The triarii carried long spears and formed the most heavily protected element. A contested landing could require them much earlier to drive defenders back.
Chapter · 40:07-41:42
Roman heavy infantry as amphibious assault armour
Roman landing doctrine illustrates how light troops secure space before armoured veterans drive defenders away from the shore.