Both Barack Obama or John McCain want to send many more American troops to Afghanistan to try to pacify the country and wipe out al-Qaida and the Taliban. Defense Secretary Robert Gates agrees, backing a $20 billion plan for major increases in the size of Afghanistan’s army and many more Western troops. This could be a mistake.

An Afghanistan troop surge matches the thinking of a reported 60 percent of Americans. The war in Iraq is dragging into its sixth year, while Osama bin Laden’s al-Qaida, the perpetrator of the September 2001 terrorist attacks, thrives and plots in the mountainous Pakistan-Afghanistan border country and its ally, the Taliban, again rules parts of Afghanistan.

Whether Sen. Obama or Sen. McCain becomes president, their prescriptions for more troops fit a broad popular demand to punish the 200l terrorists and bring law and order to the country where the trouble started. Both of them look toward victory and peace with honor in Afghanistan.

Such rosy hopes, attractive as they are, fly in the face of the historic British and Russian failures in the same country and the American failures in nation-building in a series of foreign adventures including the Vietnam war.

Time magazine’s misleading July 28 cover headline, “Afghanistan: The Right War,” actually features a warning by Rory Stewart, a former British foreign ministry official in Afghanistan, who now works in Kabul, that expansion of the U.S. military presence there is the wrong idea. He predicted that ultimate military victory over the Taliban would require hundreds of thousands of troops. U.S. Army Gen. Dan McNeil, former commander of NATO forces, has put the number at 400,000.

Instead, Mr. Stewart called for a reduced U.S. combat force. He said an increase could inflame Afghan nationalism “because Afghans are more anti-foreign than we imagine,” and the Taliban can portray itself as defending Islam and Afghanistan against foreign military occupation. He urged more effective aid to the Afghan government and a limited military strategy focussed on counter terrorism — not counterinsurgency — and on continuing to prevent al-Qaida from establishing training camps in Afghanistan.

Another area specialist, Bartle Breese Bull, foreign editor of Prospect magazine, agrees, minimizing even a Taliban-ruled Afghanistan as a threat to American security. He argued in the New York Times that al-Qaida did its flight training in Florida and planned its Sept. 11 attacks in Hamburg, not Afghanistan. He wrote that only a light U.S. presence would be needed to spot any new terrorist threats in Afghanistan and eliminate them.

Helping the Afghans create a well-governed and prosperous country rather than trying to do it for them seems reasonable. A U.S. military surge could start off a massive, long-lasting war that will end in failure. Our next president should think twice before taking that course.