To talk about casualties if war, WW2 was very costly but a lot of that was politically motivated. They built bombers and flew them to the Pacific theater and a significant percentage of them never lasted long enough to complete the journey. They put guys in planes and sent them to die in the ocean. Buy more planes! And D-Day. They sent thousands of men into direct machine gun fire with the only plan being the enemy can’t kill all of them so if we send enough men the enemy will run out of bullets. Monday quarterback and all but maybe it could have been done differently.
Afghanistan broke the Soviet Union and it could break us. We should never have gone there in the first place. The 9/11 terrorists were from Saudi Arabia. Osama bin Laden was living in Pakistan. Where is Afghanistan in all this?
The reason we won WWII is the enemy made more mistakes than we did.