The planes began flying over Grenada around dawn, their low rumble awakening people in the tiny Caribbean island where a military government had seized power days before and executed the prime minister.

More than 7,000 U.S. Marines and Army paratroopers invaded the island to the cheers of Grenadians, who commemorate the 1983 action with a national holiday known as “Thanksgiving Day.” About 100 people died during the operation dubbed “Urgent Fury.”

Dozens of U.S. veterans, Grenadians and former U.S. students evacuated from Grenada’s medical school during the operation gathered Friday to celebrate the 30th anniversary of one of the most popular foreign invasions in recent history and what was then the largest U.S. military operation since the Vietnam War.

“The U.S. stemmed the flow of blood, for which we are eternally grateful,” said Grenada Prime Minister Keith Mitchell as he spoke at a Thanksgiving Day church service. “It is because of that we can enjoy democratic principles, which we sometimes take for granted.”

Months before the operation, former President Ronald Reagan had complained about Soviet-Cuban militarization of the Caribbean and expressed worries that a new Cuban-backed 10,000-foot runway in Grenada would be used by Soviet military planes.

Then on Oct. 19, 1983, Grenada’s Marxist Prime Minister Maurice Bishop, three members of his Cabinet and four others were executed by a radical faction of his Cuba-backed party on orders of then-Deputy Prime Minister Bernard Coard.

Six days later, Reagan sent in U.S. troops, helped by a few hundred Caribbean security forces.

Reagan said the invasion was necessary to protect the lives of the more than 600 U.S. students at St. George’s University School of Medicine, but the U.N. and countries including Britain and Canada accused the U.S. of violating international law.

Charles Modica, the medical university’s chancellor, said he had polled students and found that some 90 percent did not want to be evacuated.

“I had a very negative reaction,” he said of the invasion. But his opinion softened when he saw how people responded.

“Thanksgiving Day here is more meaningful than you’ll ever know,” he said. “You have to be here to recognize how important it is to people.”

In the first few hours of the invasion, dozens of military personnel jumped out of planes with instructions to evacuate students.

“We weren’t supposed to be on the island any more than a few hours,” recalled retired U.S. Army Sgt. Maj. Scott Breasseale. “But we all know things don’t go how they’re supposed to once the first gun is fired or if intelligence changes.”

Breasseale said the highlight of the invasion for him was watching students board the helicopters.

“I saw how happy they were and the hugs they were giving each other,” he said. “I felt so much pride.”

The worst for Breasseale came on the third day of the invasion: He was in one of four helicopters leading the pack, and three crashed behind him as they landed, killing everyone.

“We flew into a very harsh situation,” he said. “There was some enemy fire, some pilot error, some tactical decisions that were probably not the best. … It’s something I’m going to carry for the rest of my life.”

Breasseale said he planned to visit the place where the fatal crashes occurred. It was his first time back in Grenada since the invasion, and he wanted to pay tribute to those who died.