Republicans held the White House during the U.S. Civil War (or War of Northern Aggression for my southern friends) - a lot of casualties there. Nixon was in the White House for a large chunk of the VietNam war although JFK clearly created the hot part of the conflict. Bush I had the Gulf War (with very limited casualties) and Reagan fought a few skirmishes as well.
I don't think casualties are the real issue. The difference in the Democrats then and now is that the current group opposes any use of our military where it could in any way, shape or form protect American interests or make this a safer place to live. At one time I think a large part of the Democratic Party actually loved America - I don't think that's true anymore.