Fight as one and die as one; Even today, the shield wall is used by military and police in riot control because it's just that effective. Train for thirty years with your katana but I'll bring you down with ten disciplined men with a few weeks of training and the right cooperative weapons.
Forensic scientists have examined the corpses of ancient battlefields. The average Roman legionnaire was 5'4" tall and the average German warrior was 5'9 1/2", the same height as the average modern American male. Regardless of the disparity in physical prowess, the disciplined military always beat the warrior when they faced off on equal terms.