A U.S. Marine lieutenant, Robert Paz, took a wrong turn into a Panamanian Defense Forces checkpoint in Panama City. PDF soldiers opened fire, killing him. That shooting, on December 16, provided the final pretext. At 12:45 AM on December 20, Operation Just Cause commenced. The first objective was the seizure of the Bridge of the Americas over the Panama Canal. Rangers from the 75th Ranger Regiment fast-roped from helicopters onto the Pacora River bridge east of the city, expecting heavy resistance. They found only a startled PDF sentry, who fled.
The invasion involved over 27,000 U.S. troops. Their primary missions were to capture Noriega, protect American lives, and secure the canal. Fighting was intense but lopsided. Key PDF headquarters were destroyed by precise airstrikes and armor. Noriega evaded capture for four days, eventually seeking sanctuary in the Vatican's diplomatic mission. U.S. psychological operations troops surrounded the nunciature and blasted rock music at deafening volumes. He surrendered on January 3, 1990, and was taken to the United States to stand trial on drug trafficking charges.
The operation is often framed as a neat success. It was militarily decisive but politically messy. The U.S. recognized a new Panamanian government within hours, but civilian casualties were significant. Estimates range from several hundred to over a thousand Panamanian deaths. The invasion violated international law, drawing condemnation from the Organization of American States and the United Nations General Assembly.
Noriega's removal ended his regime but did not instantly stabilize Panama. The legacy is a case study in the blunt instrument of unilateral military intervention. It achieved a specific tactical goal—regime change—while leaving complex questions about sovereignty, collateral damage, and long-term nation-building largely unanswered.