2. Vietnam War (1955-1975)
The Vietnam War escalated as the U.S. Congress passed the Gulf of Tonkin Resolution in 1964, granting President Lyndon B. Johnson authority to use military force in Southeast Asia without a formal declaration of war. This legal framework led to extensive troop deployments, bombing campaigns, and significant casualties, setting a precedent for future American military engagements without official declarations (britannica.com).
