The 1,000 man legion

[Robert Vermaat]

This makes more sense that 1000 men was the described standard but not an absolute that was 100% enforced. As I mentoned in my initial post while this would work well when dealing with barbarian raiders in Gaul it would be devestating to Roman effectiveness if used against Persia.

Not at all. The number of men in a single unit were lowered as a standard unit, but that did have no effect on the strenght in a battle. The LR army combined two units (like modern regiments) to form a pair that usually went into battle together. You just have more units in an army, even when the total number remains the same. This reflects a different way of fighting, for which the legion simply was too large. Recall that the large legions aready had begun sending vexilia to other places where men were needed, or lots of vexilia to form expeditionary forces - this practise became the bais for smaller units but was essentially the same.

Modern armies did the same with 'battle groups' (Task Forces, Kampfgruppen), where smaller groups are detatched from a larger force to undertake a specific task. Or does the US army still go into battle with whole divisions?