The enemy commanders probably think the same way.
After a brief pause a horn sounded.
The enemies' advance hastened at the same time.
One group of enemies slowly pick their way through, another constructs a bridge, others occasionally falling into a pit or detouring around one. In this way they advance a tiny bit at a time.
Having seen the archer's attack they now advance boldly without fear of a magic attack.
Well, that should be enough.
"Magic troop prepare."