In one of those curious rhymes of history, Trump faces a similar challenge to Truman’s in confronting North Korea. Truman went to war in 1950 to reverse a North Korean invasion of the South. Trump is now perilously close to conflict in his attempt to halt North Korea’s defiant nuclear program (emphasis added).
War Powers. Article I, Section 8, Clause 11 of the U.S. Constitution grants Congress the power to declare war. The President, meanwhile, derives the power to direct the military after a Congressional declaration of war from Article II, Section 2, which names the President Commander-in-Chief of the armed forces.
The United States Congress has not formally declared war since World War II. All of our wars in the Middle East have been authorized using other means, which rather goes to the heart of the nature of those different conflicts. U.S. entry into World War I and World War II took place through joint congressional resolutions stating "a state of war exists between the Government of Country X and the Government and People of the United States," where country X was, variously, Germany, Japan, Italy, and so on.
It would be impossible to write such a sentence about Syria today. In what meaningful way does a state of war exist between the United States and Syria? None. That's why Congress, if it approves anything, will approve an authorization for the use of force. And if history is any guide, that's going to be a rather open-ended commitment, as fuzzy on the back-end as on the front.
[Furthermore], America has done a better job of winning its declared wars in the last century than achieving clear-cut victories in ventures authorized under legislative measures that fell short of a formal declaration of war.