<P> The legions of the late Republic were, structurally, almost entirely heavy infantry . The legion's main sub-unit was called a cohort and consisted of approximately 480 infantrymen . The cohort was therefore a much larger unit than the earlier maniple sub-unit, and was divided into six centuries of 80 men each . Each century was separated further into 10 "tent groups" of 8 men each . The cavalry troops were used as scouts and dispatch riders rather than battlefield cavalry . Legions also contained a dedicated group of artillery crew of perhaps 60 men . Each legion was normally partnered with an approximately equal number of allied (non-Roman) troops . </P> <P> However, the most obvious deficiency of the Roman army remained its shortage of cavalry, especially heavy cavalry . As Rome's borders expanded and its adversaries changed from largely infantry - based to largely cavalry - based troops, the infantry - based Roman army began to find itself at a tactical disadvantage, particularly in the East . </P> <P> After having declined in size following the subjugation of the Mediterranean, the Roman navy underwent short - term upgrading and revitalisation in the late Republic to meet several new demands . Under Caesar, an invasion fleet was assembled in the English Channel to allow the invasion of Britannia; under Pompey, a large fleet was raised in the Mediterranean Sea to clear the sea of Cilician pirates . During the civil war that followed, as many as a thousand ships were either constructed or pressed into service from Greek cities . </P> <P> The Constitution of the Roman Republic was a constantly - evolving, unwritten set of guidelines and principles passed down mainly through precedent, by which the government and its politics operated . </P>

The end to the roman republic occurred when