As fighting continues between Israel and Hezbollah, both the British government and the United Nations have called for the dispatch of an international peacekeeping mission to southern Lebanon. "The only way we are going to have a cessation of violence is if we have an international force deployed," British Prime Minister Tony Blair said on Monday. UN Secretary General Kofi Annan added that such a force is "essential."

But with its long and troubled history in the region, the idea of sending a peacekeeping force should be dead on arrival.

In 1956, the United Nations deployed peacekeepers to separate the Israeli and Egyptian armies. At first the mission was successful. But in May 1967, Egyptian President Gamal Abdel Nasser sent 80,000 troops and 550 tanks to the Israeli border and demanded peacekeepers withdraw. They did. Less than three weeks later, the Six-Day War erupted. Peacekeepers unwilling to fight an aggressor and win cannot keep peace.

The UN tried again after the Yom Kippur War. In 1974, it sent a Disengagement Observer Force to separate the Israeli and Syrian armies. Butwhile the Golan Heights remained quiet, their mission was no success. Both Damascus and Jerusalem simply shifted the battleground to Lebanon.

After the 1982 Israeli invasion of Lebanon, the United States, France and Italy sent peacekeepers to Beirut to separate both Israeli and Syrian forces and Lebanon's many militias. All went well initially. But on April 18, 1983, terrorists attacked the U.S. Embassy in Beirut and, on October 23, 1983, a Hezbollah suicide truck bomber blew up the U.S. Marine barracks in Beirut, killing 241 servicemen. President Ronald Reagan promised to stand firm. "To remove them now," he said of the peacekeepers, "would undermine American credibility throughout the world." True, but he withdrew them anyway.

The Marines' departure from Beirut was a major defeat for peacekeeping. Not only would the Lebanese civil war continue for another six years, but terrorists also came to believe that the Western commitment to peacekeeping was ephemeral. In a 1998 interview, Osama Bin Laden called American soldiers "paper tigers," citing their withdrawal from Beirut as proof. That Annan yanked his staff from Iraq after the August 2003 bombing of the UN headquarters in Baghdad underscored Turtle Bay shared the same lack of resolve.

It is not only timidity that undercuts the UN's ability to keep peace, but also its susceptibility to corruption. The July 12 kidnapping that sparked the latest violence was not Hezbollah's first. On Oct. 7, 2000, more than four months after Israel withdrew from Lebanon, Hezbollah guerillas using UN vehicles snatched three Israeli soldiers. After eight months of denying they witnessed the operation, UN peacekeepers in Lebanon acknowledged having a videotape, but balked at sharing it with Israel. To do so, they argued, might "undermine UN neutrality." Hezbollah executed the prisoners. And Israel learned an important lesson about trusting peacekeepers.

There is one exception though to the peacekeeping curse. The Multinational Force and Observers have for 25 years kept peace in the Sinai. Their secret? They came not to end a war, but only after a peace treaty was agreed to. But as long as Hezbollah, Syria and Iran seek to wipe Israel off the map, peacekeeping will fail.

Rubin, a resident scholar at the American Enterprise Institute, is editor of the Middle East Quarterly.