But, as you point out, there's that "nature" thing. Because of the conditions on Navy ships on long deployments, they are probably the best/worst example. It's amazing what percentage of the crew (they are still member's of the crew) become not fit for duty/full duty due to some collateral torpedo damage.
Then there's the whole protection instinct issues for the ground troops...the Isrealis' found out it didn't work and pulled women out of combat units (in a nation that needs every fighting person it can field).