|The Seal of Office of the United States War Office|
Under George Washington, the Secretary of War was Henry Knox. He had been the chief artillery officer of the Continental Army, and before the ratification of the constitution, he served as the Continental War Secretary.
At first, the Secretary of War was responsible for all military affairs, but in 1798 the separate position of Secretary of the Navy was created, and the Secretary of War's scope was reduced to cover only the army. After 1886, the Secretary of War was third in line of succession to the presidency, right after the Vice President and the Secretary of State. (I bet Al Haig knew that!)
Something rather big happened to the Secretary of War position in 1947, with the passage of National Security Act of 1947: the Office of Secretary of War entirely disappeared. According to the Wikipedia: "The Secretary of the Army's office is generally considered the direct successor to the Secretary of War's office although the Secretary of Defense took the Secretary of War's position in the Cabinet, and the line of succession to the presidency."
Why? Why did they do that? By eliminating the word "War" from the name of the office, did we eliminate war? No. There have been lots of wars in which the United States was involved since 1947. But none of them have been declared! This means that the Executive Branch has been free to wage war without the consent of the other branches ever since the word "war" was eliminated from our respectable statesman-like vocabulary.
Change the linguistic context, and you change the meaning of the constitution. Apparently, the requirement for a declaration of war went away as soon as we stopped calling it war.
Today, everybody seems to agree that war is a bad thing and we should avoid war at all costs. Everyone gives lip service to this idea. And yet it is easier for the president to start a war than ever before!
Reframing the context is a very dangerous thing. It would be better if we still called it war and had open discussions about when it should be declared and who should pay for it and who should be asked to risk life and limb in waging it.