The constitution is what ever the judges say it is. Presidents have committed troops to War in Korea, Vietnam, the Gulf, Kosovo and Afghanistatn with out a declaration of war. And the Supreme Court has refused to even hear a case about it. The supreme court will hear cases it thinks have constitutional issues. (See presidential election in Florida 2000) That was a constitutional issue and the justices heard it. War with out a declaration of war is not an issue and the justices refuse to even consider it.
I never once said "declaration of war" was required.