Giving up that idea is hard to do in Washington, even for presidents. It requires them to defy powerful pressure.
Mr. Obama should recall that in 1962 President Kennedy instinctively resisted Defense and State Department pressure to send more troops to Vietnam. President Johnson was also wary of a troop buildup in Vietnam, but he fell prey to his own fears that Republicans would accuse him of being soft on communism if he flinched in the face of a festering Viet Cong insurgency.
America has a poor record of nation-building abroad. The George H.W. Bush administration and Clinton White House failed in Somalia. The most recent Bush administration bungled it in Iraq, where Iraqis continue to blow one another up now that Americans are increasingly out of reach as targets.
And now, bright as he is, Obama is showing us he learned next to nothing from the nine-year Soviet attempt at nation-building in Afghanistan that helped hasten the collapse of the Soviet Union.