that wars fall into two categories. You just can't tell which one you're in until it's over. Joe Haldeman's "The Forever War" is a fictional example of the other. Not that I blame Heinlein for ST, if our fight with the Bugs had just been a a misunderstanding, the book would have been a tragedy, not heroic fun. Look at our own country's historical record of DECLARED wars (staying safely in the past) and forgetting about our numerous skirmishes, police actions and other unpleasantries.

The War of Independence was certainly justified, although Canada's example suggests that if it never had happened we would have gotten our freedom from Britain anyway.

The War of 1812 was a farce, we got our butt kicked primarily because we were selling stuff to both the French and English and the latter had a navy and tried to stop us. We finally won that one at New Orleans, but it wasn't until AFTER the peace had been signed.

The Mexican War was naked aggression on our part and a national disgrace.

The Civil War had to be faught, although again, history suggests that if we could have held off a few years the causative issues would have settled themselves on their own.

The Spanish American War was another shameful war of imperialism.

World War I should never have been faught at all, by anyone, and we had no business getting involved.

World War II was certainly justified as a response to aggression and to remove Fascism from the world.

After that, no one anywhere has formally declared war on anyone else, so that looks like a good place to stop.