"Nearly every U.S. president—43 out of 45 who served full terms—has used military force without a formal congressional declaration of war. While only 5 wars were formally declared by Congress, presidents have initiated military actions over 125 to 168 times without prior explicit authorization, notably increasing since World War II.

Pre-WWII Examples: Early presidents like Washington, Jefferson, and Adams took military action against foreign adversaries or tribes without formal declarations.
Post-WWII Escalation: Major conflicts like Korea, Vietnam, and subsequent actions in Iraq and Afghanistan were handled under executive authority rather than formal declarations.
Modern Era: Since the 1973 War Powers Resolution, every president has authorized military actions (e.g., in Grenada, Panama, Iraq, Kosovo, Libya, Yemen) without prior congressional approval, often relying on Article II authority.
Exceptions: Only William Henry Harrison and Zachary Taylor are typically cited as having no significant military engagements, often due to their brief time in office.
Controversy: Critics argue this trend, including actions by presidents from Truman to Trump, bypasses constitutional checks.

Commonly cited examples of unilateral action:
Harry Truman: Initiated the Korean War, calling it a 'police action.'
Lyndon Johnson: Escalated Vietnam following the Gulf of Tonkin Resolution.
Bill Clinton: Led engagements in Bosnia and Kosovo.
Barack Obama: Ordered military strikes in Libya.
Donald Trump: Ordered the 2020 strike against Soleimani in Iraq."