The correct answer is the Executive Branch.
The war powers act placed limits on the power of the Executive Branch.
The War Powers Act limits the ability of the president of the United States to initiate military actions in other countries. This resolution of Congress requires that the president notifies the Legislative branch to approve any action. The Act was enacted in 1973 tried to prevent situations like the Vietnam War. The President is the Commander in Chief of the Military Forces, but the Legislative has the faculty of declaring war.