This mission can be surprisingly difficult. The gray and red soldiers, when clumped, are pretty much impossible to fight toe to toe with since half of them do low sweep combos, and the other do high. Run around picking off stragglers to build chi, and use chi moves to take down the grays first, and then focus on the little reds.
Once the big guards spawn, use the bombs from the rebels against them. They will constantly shoot shockwaves at you, but you can only block one at a time. Stay moving constantly. Try to separate a guard from the rest and lock him down with chi moves.