"(O)nce war is forced upon us, there is no other alternative than to apply every available means to bring it to a swift end.

"War's very object is victory, not prolonged indecision.

"In war there is no substitute for victory."

Familiar to every graduate of West Point, the words are from the farewell address of Gen. MacArthur, to Congress on April 19, 1951, after he was relieved of command in Korea by Harry Truman.

Two years later, however, Dwight David Eisenhower, a general as famous as MacArthur, would agree to a truce that restored the status quo ante in Korea.

For the first time since the War of 1812, the United States was not decisively victorious. We had preserved the independence of war-ravaged South Korea. But the North remained the domain of Stalinist strongman Kim Il-Sung for 41 years.

After Korea came Vietnam. The United States did not lose a major battle and departed in early 1973 with every provincial capital in South Vietnamese hands. But the war was lost in April of 1975, when Saigon, its military aid slashed by Congress, fell to an invasion from across the DMZ.

Vietnam introduced us to what no generation of Americans save Southerners had ever known: an American strategic defeat.

Now we are about to enter our eighth year in Afghanistan and our sixth year in Iraq. In neither is victory, in the MacArthurian sense, assured. Indeed, "victory" may be unattainable, says America's most successful general, David Petraeus, who asserts he will never use the word in speaking of Iraq. "This is not the sort of struggle where you take a hill, plant the flag and go home to a victory parade."

Why will Operation Iraqi Freedom not end like Gulf War I, where Gen. Schwarzkopf led the victorious army up Constitution Avenue? Because, whenever a truce is achieved through power-sharing, it often proves to be the prelude to a new war, when the power shifts.

In Iraq, the Shia-Sunni struggle remains unresolved. The Maliki regime wants the Americans gone so it can settle accounts with the Awakening Councils and Sons of Iraq we armed to eradicate Al-Qaida. The Kurds are moving to cement control of oil-rich Kirkuk and expand into Iraqi Arab provinces.

Of that other war over which he has assumed command, Gen. Petraeus says: "Obviously the trends in Afghanistan have been in the wrong direction. ... You cannot kill or capture your way out of an insurgency that is as significant as the one in Iraq, nor, I believe, as large as the one that has developed in Afghanistan."

"We can't kill our way to victory," adds Adm. Michael Mullen, chairman of the joint chiefs. We are "running out of time."

Mullen earlier said he's "not convinced we're winning it in Afghanistan."

The British commander, Brigadier Mark Carleton-Smith, is even gloomier. The British people, he says, should not expect a "decisive military victory. ... We're not going to win this war. It's about reducing it to a manageable level of insurgency that's not a strategic threat and can be managed by the Afghani army."

Carleton-Smith is euphoric alongside Sir Sherard Cowper-Coles, ambassador in Kabul, who is quoted in a letter to the prime minister as saying NATO strategy in Afghanistan is "doomed to fail."

Before either a President Obama or McCain sends 10,000 more troops into Afghanistan, he should conduct a review as to whether this war is winnable, and at what cost in blood, money and years.

Afghanistan is the longest war in U.S. history. Why have we not yet won? First, because we lack the forces. In World War I, we put 2 million men in France in 18 months. In World War II, 16 million served, with 12 million in uniform at war's end. Today, we have 31,000 U.S. troops in Afghanistan.

Why so few troops? Because, despite what Americans say, few truly believe the survival of the Hamad Kharzai regime is vital to our security or that we would be in mortal peril should the Taliban return. Indeed, Petraeus says we should seek "reconciliation," presumably with the more moderate of the Taliban.

Converting enemies into allies with bribes or access to power may not be as dramatic as a Marine flag-raising on Mount Suribachi. But if reconciliation can end these wars successfully -- assure us neither nation is used as a base camp for terror -- would that be unacceptable? As Sun Tzu wrote, the greatest victories are those won without fighting.

For America's great wars, MacArthur and Eisenhower were the right generals. For today's wars, where the threat is not mortal and there will be no surrender signing in a railway car at Compiegne or on the deck of a battleship Missouri, Petraeus seems the right man -- and appears to have no need of an Eisenhower jacket or corncob pipe.