Actually, Troll's got a good point.

The executive branch, and the military, chose to fight a war without any declaration of war, because, first, who would they have declared war on? North Vietnam? As I recall, they denied its existence as a sovereign nation. And, second, they weren't sure they could get a declaration of war out of Congress. So had no basis for a charge of treason, if they wanted to bring one. They kind of painted themselves into a corner. One of many that they painted themselves into in that period.

Peter.