In higher level online play, people use skirms to pad their numbers or screen for heavy cavalry. JinandJuice and Paul are rather good and annoying at this with their skirmisher/crap levy following directly behind their cavalry to give them a place to retreat back to.
You should try and run them past the enemy's right flank(your left side) so you can hit them in their sword side(no 2x shield bonus vs missiles) :-p.
Another good tactic vs barbarians(who for the most part suck with missiles) is to keep a giant stack of them behind your main line to rain missiles over the front line and then use them to help your units resist scary naked units or you can use them to flank and surround the big scary ball of men that people onlien and the AI tend to send at you.
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