I've tried the first mission about a dozen times now- the very first intro mission- and I can't get past it. It's 3 on like 75 and while you only have to fight like 9 of those guys, I can't do it. I've tried every trick in the book. You can't stop and heal because you always have an enemy behind you, your guys all drop in like 3 hits. What am I missing? I've tried it over and over and over.