4000 in WWII. They deployed with about 16000.
I would have hated to be in the Marine companies in the Battle of Tarawa that suffered over 70% casualties.
But I would have hated being in the 8th Air Force as well. In terms of casualties.
I was at a commemoration event on Guadalcanal in the Solomon Islands back in the '80's. There were some surviving US Marine veterans of that battle there with us. All of them suffered from malaria. They were also surprised how "built up" the island had become. I could only see one building in the area, operated by some Australians.