I think in technical areas (pilots, sailors, doctors, nurses, etc.), where there is no direct physical to physical conforentations, women should definately be allowed in. But in 'grunt' types of conflict, they should absolutely not.
Not only are women physically smaller then males, for the most part, and not able to physically compete, but in wartime situations, there can be some pretty nasty complecations. Everything from using the loo, to sleeping in foxholes can be akward for both male and female, to say the least. Then there's the whole danger of mistreatment by males in the unit (sexual harassment) or even worse, abuse by the enemy (rapes, etc.)