AP Photo

While American attention has drifted to Haiti, a failing state heart-wrenchingly close to home, Hamid Karzai's ramshackle government in Afghanistan is still very much in the crosshairs of the resurgent Taliban. On Monday, the Taliban demonstrated that even the safest corner of the country, the administrative heart of Kabul that is home to the fortified presidential palace and the central bank, is terrifyingly vulnerable. Though only a handful of Afghans died, dozens were injured in a suicide attack that will not-so-subtly change the calculations not only of Afghans but of the thousands of American and European civilians that the country badly needs to rebuild its battered institutions. Indeed, this attack follows successful attacks against a U.N. compound last fall that rattled the...