If President Barack Obama supports the recommendations of Stanley McChrystal, the general he picked to run the war in Afghanistan, he'll have done a very brave thing. The president, in pushing for a health-care plan a majority of Americans really don't want, has shown he'll go against public opinion. But he's never opposed his base. If Mr. Obama supports Gen. McChrystal's request for 40,000 more troops, he'll be bucking both.

If he does, will he be doing the right thing?

Afghanistan is a mess not of Mr. Obama's making. We went to war in Afghanistan because the Taliban government was providing shelter to al-Qaida. After the Taliban was routed in a brilliant campaign utilizing special forces and air power, and after surviving al-Qaida largely relocated to Pakistan and Iraq, President Bush shifted the mission to nation building in a country that has never been a nation in the modern sense.

Lt. Col. Ralph Peters, a retired Army intelligence officer, illustrated the foolishness of this with an analogy: "A pack of murderous thugs holes up in a fleabag motel. The feds raid the joint, killing or busting most of them. But some of the deadly ringleaders get away. Should the G-men pursue the kingpins, or hang around to renovate the motel?"

Lt. Col. Peters wants to ditch the nation-building and focus on killing bad guys.

"What we really need is just a compact, lethal force of special operators, intelligence operators and air assets, along with sufficient conventional forces for protection and punitive raids," he said.

I'm inclined to agree. The difficulty is that there is no greater expert in the U.S. military on this strategy than Gen. McChrystal, a Green Beret and Ranger who, as head of the Joint Special Operations Command, nailed Abu Musab al-Zarqawi, the notorious al-Qaida commander in Iraq. And Gen. McChrystal has concluded it won't work.

"There is clearly a role for precise operations that keep the insurgents off balance," Gen. McChrystal wrote Aug. 26. But these operations can only "be effective when the insurgents have become so isolated from the population that they are no longer welcome, have been kicked out of their communities and are reduced to hiding in remote areas and raiding from there."

Another problem with the strategy I favor is that while it certainly would have been better than what President George W. Bush did, Mr. Bush did something else that changes the calculus. To withdraw a large number of troops from Afghanistan would be perceived as a defeat, and the perception of defeat can have consequences as ugly as defeat itself.

When asked what he thought of a U.S. withdrawal from Afghanistan, Pakistan's foreign minister told The Wall Street Journal "this will be disastrous. You will lose credibility ... Who is going to trust you again?"

Vice President Joe Biden reportedly is pressing for a dumbed-down version of the Peters/Kelly strategy in which almost all American forces would be moved "offshore," and reliance for anti-terrorist strikes placed on aircraft and Predator drones. This strategy was outlined by conservative columnist George Will in a column Aug. 31.

The political appeal of this approach is obvious. But it is militarily puerile. Lt. Col. Peters explains: "We still need some boots on the ground, within grabbing distance of Pakistan's wild northwest to strike fast to kill or capture elusive targets. And cruise missiles can't bring back prisoners, DNA samples or captured documents."

The fundamental problem in Afghanistan is that neither presidents Bush nor Obama recognized that Afghanistan is just one battlefield in a global struggle against a transnational terror group and its state sponsors.

"Our problem with Bush is that for seven years he never really examined a badly flawed strategy in Afghanistan," a "senior British official" told The New York Times. "Our problem with Obama is he keeps questioning what we're trying to accomplish."

"What in Afghanistan is deemed our nation's vital interest?" Gen. Charles Krulak, a former commandant of the Marine Corps asked rhetorically in an e-mail to George Will. "Who is the enemy? Is the enemy of the United States the Taliban? Is the enemy al-Qaida? We need to determine the answer to those questions immediately. One would think we would have answered them already but none of our actions to date would indicate that we have."

Jack Kelly and Reg Henry spar on the topics of the day exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.