As the Grenada operation was being hurriedly planned at the Pentagon, service rivalries reared their head. All branches of the armed forces insisted on participating. The result was a cobbled-together force that led to everything from shouting matches between officers to the discovery that each service used different radio frequencies and could not reach the others.

There was no easy way to repair this damage, and Reagan quickly ordered U.S. troops to abandon Lebanon. But by felicitous coincidence, the attack happened at the same time that Bishop's executioners in Grenada were trying to consolidate their new regime. Reagan had ordered preparations for an invasion before leaving Washington for his golfing weekend. He gave the final go-ahead after the Beirut attack.

Reagan had come into office pledging to restore American glory and was looking for a place to flex the country's military muscle. He had sent Marines to intervene in Lebanon's civil war, but that had not provided the quick victory he wanted. He was spending a weekend at Augusta National Golf Club when, at 2:27 on the morning of Oct. 23, he was awakened and given one of the worst pieces of news he would hear as president. The Marine barracks in Beirut had been destroyed in a suicide-bomb attack, killing 241 servicemen.

In 1979, a handful of leftists calling themselves the New Jewel Movement seized power in Grenada. Their charismatic leader, the British-educated Maurice Bishop, turned out to be an admirer of Fidel Castro. Some of his comrades, however, considered him insufficiently radical. In October 1983, they deposed and executed him. That gave Reagan his chance.

Timing was the reason President Ronald Reagan launched the invasion. Americans were still demoralized from their defeat in Vietnam and the humiliating hostage crisis in Iran. Marxist-led insurgents had seized power in Nicaragua and were ascendant in El Salvador and Guatemala. A senior British officer who watched the Grenada invasion from nearby Barbados, Maj. Mark Adkin, wrote afterward that it was launched because of "the intense desire of the president and his advisers to raise U.S. prestige, particularly at home and in the armed forces, where morale and self-respect had fallen substantially since Vietnam."

Grenada is a lovely dot of real estate. Natives like to say it is "just south of paradise, just north of frustration." Its population at the time of the invasion was 90,000, equivalent to that of Fargo, N.D. In 1983 one of the oddest battles of the Cold War was fought there.

American troops who hit the beaches on the tiny Caribbean island of Grenada exactly 30 years ago were bit players in a geopolitical comic opera. The invaders used photocopies of tourist maps, since the U.S. military had no maps of its own for the country. Communication was so confused that one officer had to call his base in North Carolina from a pay phone to request air cover. After an American bomb was mistakenly dropped on a mental hospital, dazed patients wandered aimlessly as heavily armed fighters emerged from surrounding cinnamon and allspice plantations, lending a surreal quality to the operation.

At first, Reagan seemed uncertain about whether to call for the invasion. His first order was to send only a warship, in case American students on the island requested evacuation. "There are not going to be any landings or anything like that," a Navy spokesman assured the press on Oct. 21. Four days later — two days after the Beirut bombing — the first of what became more than 7,000 U.S. troops stormed ashore.

On the morning of Oct. 25, Prime Minister Margaret Thatcher of Britain, which considered itself the ultimate legal authority in Grenada because the island is part of the Commonwealth, warned Reagan that an invasion "will be seen as intervention by a Western country in the internal affairs of a small independent nation, however unattractive its regime."

"She was very adamant and continued to insist that we cancel our landings on Grenada," Reagan later wrote in his autobiography. "I couldn't tell her that it had already begun."

The invading force met light resistance, including from a small cadre of Cubans. Nineteen Americans were killed. Within days, New Jewel leaders had been rounded up, and Grenada was quiet again. U.S. troops departed a couple of months later.

In public, Reagan and his aides justified their invasion with three arguments. First, they depicted Grenada's regime as murderous, anti-American and supported by Cuba. This was true, but it did not make Grenada a threat to the United States. Second, they said they needed to protect the lives of American students, although the students did not appear to be in danger. Third, they produced a letter signed by the governor general of Grenada, Paul Scoon, asking for intervention. It later turned out that the letter had been written in Washington, backdated and delivered to Scoon to sign after the invasion began.

The real reason for the operation was Reagan's belief that the U.S. needed a victory — any victory, anywhere. After the United Nations passed a resolution condemning the invasion as a "flagrant violation of international law," he brushed it off by saying that the resolution "didn't upset my breakfast at all." Several members of Congress visited Grenada to bask in the glory, among them Rep. Dick Cheney of Wyoming, who said the invasion proved that the United States was once again "steady and reliable."

An orgy of self-congratulation followed the triumph. A total of 8,612 medals were awarded to participants — most of them to desk officers who never came within a thousand miles of the island. "Our days of weakness are over!" Reagan exulted in a speech to the Congressional Medal of Honor Society in New York. "Our military forces are back on their feet and standing tall."

The invasion of Grenada was code-named Operation Urgent Fury, but it was neither urgent nor furious. It was carried out mainly to serve perceived political needs inside the United States. Geostrategic reasons were secondary. The United States subdued a nation whose entire population could have fit inside the Rose Bowl in Pasadena, Calif. That this thrilled so many Americans suggests the enduring appeal of military victory, no matter how small or insignificant.

The Reagan administration never made any attempt to negotiate with Grenada's leaders or to evacuate American students peacefully. Its goal was not to resolve a tense situation but to destroy a regime that Reagan said was planning to "export terror and undermine democracy." The same approach would be used six years later in Panama, where the United States rejected a plan by the National Guard to depose the strongman, Manuel Antonio Noriega, because it wished not only to remove a leadership group but also to wipe out an entire governing system that it considered hostile.

Operation Urgent Fury was also an extreme example of asymmetric warfare. It was meant above all as a show of force, and it stunned the Central American and Caribbean left. Inside the Reagan administration, it was seen as a triumph. It gave senior officials a sense of momentum, which propelled them to intensify U.S. support for pro-U.S. regimes in El Salvador and Guatemala and for Contra rebels fighting the Sandinista government of Nicaragua.

One final legacy of this invasion is what did not happen afterward. It would have been cheap and simple for the United States to turn Grenada into a model of Caribbean prosperity and thereby to suggest that being conquered by Americans is a good thing. Instead, the U.S. quickly moved on. In 2007 Grenada co-hosted the Cricket World Cup in a brand-new $40 million stadium. It was paid for by the People's Republic of China.