Armed with javelins for harassing enemy formations they can cause a surprising number of casualties. They do poorly at melee and are best used only as skirmishers.
Can Hide in Long Grass
Armed with nothing but a small shield and a handful of javelins these men risk their lives in closing with the enemy with only the lightest of equipment. These men deploy in a cloud before the heavy infantry dashing back and forth to release their deadly missiles. These infantry skirmishers fought in open formations so as to maximize the number of men able to get a throw and minimize the effect of enemy missiles. Lacking armour, training and heavy weapons these light infantry stand no chance if committed to melee.
Historically, most armies of the classical period found use for poorly equipped levies as skirmishers, very often as javelinmen, as these troops required relatively little training and financial investment, relying mostly on widespread natural skills and scant gear, while still providing some useful service.