What entity has the power to declare war?

The entity that has the power to declare war is Congress. According to the U.S. Constitution, specifically Article I, Section 8, the power to declare war is explicitly granted to Congress. This is a crucial feature of the system of checks and balances designed by the framers of the Constitution, as it prevents any one individual, namely the President, from having the unilateral authority to engage the nation in armed conflict without legislative approval.

The framers intended that the decision to go to war would reflect the will of the people, articulated through their elected representatives, which is why Congress holds the power. While the President, as Commander-in-Chief of the armed forces, has the authority to direct military operations, any formal declaration of war must originate from Congress. This ensures that such a grave decision is made with broad consensus rather than through executive action alone, maintaining the balance of power among the branches of government.