Which level of government can declare war on foreign Nations​

The Constitution of the United States divides the war powers of the federal government between the Executive and Legislative branches: the President is the Commander in Chief of the armed forces (Article II, section 2), while Congress has the power to make declarations of war, and to raise and support the armed forces (Article I, section 8). Over time, questions arose as to the extent of the President's authority to deploy U.S. armed forces into hostile situations abroad without a declaration of war or some other form of Congressional approval. Congress passed the War Powers Resolution in the aftermath of the Vietnam War to address these concerns and provide a set of procedures for both the President and Congress to follow in situations where the introduction of U.S. forces abroad could lead to their involvement in armed conflict.

Conceptually, the War Powers Resolution can be broken down into several distinct parts. The first part states the policy behind the law, namely to "insure that the collective judgment of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities," and that the President's powers as Commander in Chief are exercised only pursuant to a declaration of war, specific statutory authorization from Congress, or a national emergency created by an attack upon the United States (50 USC Sec. 1541).

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