Edit: It looks like it doesn't take pictures. If it did, you would notice that I had gotted deadly commander on all levels except for the sixth, which I haven't gotten any medals on.
i beat 6 w/ DC. all you have to do is use your towers and base health to your advantage. if they're going to deploy their little rain of fire on the first slot, throw a tower on the second one. also waiting for the slugs to get close enough to the towers before deploying is key. you'll need all your men, so don't rush at the beginning. let the hard ones hit your base and kill the easy ones.
Go right twice. Build a fortress and farm land. Get Cold steel 3 and weapons 3.
You have to beat both bases in 1 turn in order to get DC. You shouldn't need to build any more units.
Fighting requires some luck. If the first unit they send is a snake, build a tower in one of the other lanes. Wait until it is within range, then build a 2nd tower. With the upgrades your tower can kill their priest looking thing and their big melee unit. In general, the idea is to let the 2 towers take out as many units as they can while saving your real units until the end. Hopefully, a few easy units (snakes, assassins) will stack up behind one of the towers. When the tower falls, use a RG or crusader to slaughter a few low hp units.
