The vote was 47-53, largely along party lines. If passed, the resolution would have blocked further U.S. military action in Iran without congressional approval under the 1973 War Powers Act. That legislation passed during the Vietnam War to give Congress a legal check on executive war authority. The 1973 act also requires the president to notify Congress within 48 hours of deploying U.S. forces into hostilities and to end the deployment within 60 days unless Congress authorizes or extends it.