I'm trying to make a UMS survival map, kind of like horde mode in Gears of War 2 where you face increasingly powerful waves of Zerg.

After I create the Zerg units, I use the trigger action ORDER like this:

Issue order to all any unit owned by Player 1 at 'Spawn Point':
Attack to 'Human Base'.

Instead of traveling to that location while attacking everything on its way, the units go straight for that location and only stop to fight units that attack them. This becomes a problem when I start spawning flying units for the Zerg, and the majority of them go straight past a player's defenses and take out the Command Center.

I've tried several variations of Attack and Move and I just can't get them to behave that way. Any suggestions?

Thanks in advance for all help!

Use Order: Patrol

The computer or human units will attack human/computer/neutral units on the way, at the specified location (center of map if ANYWHERE) and walk back and forth when there is nothing to kill.
You can then switch the computer units to another computer player and switch back again if you want them to stop at the location.
ALSO make sure the Alliances are set to that the computer attacks the right players!
Let me know if that helps

Worked like a charm, thanks!