Final answer:
Only five of the 13 major wars fought by the U.S. have followed a formal declaration of war by Congress.
Step-by-step explanation:
Of the 13 major wars the United States has participated in, only five have been preceded by a formal declaration of war by Congress. Since the 1941 attack on Pearl Harbor, presidents have generally initiated military action without a formal declaration of war, opting instead for open-ended congressional authorizations, UN resolutions, or other forms of international support. The War Powers Resolution of 1973 sought to define and limit the president's power to engage in armed conflict without direct congressional approval, stipulating that the president must inform Congress within 48 hours of committing troops to hostile situations without a declaration of war and setting a 90-day limit for their deployment without further authorization.