Until now, pleas from the US to Mr Karzai to stem government corruption have failed to rouse him. That's why Mr Obama decided to deliver the message in person this time.
Obama sounds the alarm in Kabul visit
Since the 2003 invasion of Iraq, unannounced, middle-of-the-night visits by top American officials to regional hotspots have become regular occurrences. Security is the most obvious reason for dropping in after hours, but in the case of President Barack Obama's surprise visit to Afghanistan yesterday, we add another reason: to wake President Hamid Karzai from his slumber. Until now, pleas to Mr Karzai to stem government corruption have failed to rouse him, even when the petitioners showing up at the presidential palace in Kabul were the US secretary of state, Hillary Clinton, and the US defence secretary Robert Gates. That's why Mr Obama decided to deliver the message in person this time.
It has been clear for some time that in Washington's view, Mr Karzai just doesn't get it. In January, he pledged to make progress in cleaning up his government and making it more accountable. Since then, he has opposed anti-corruption efforts and sought to appoint warlords to his cabinet. Mr Obama can ill-afford a somnolent Mr Karzai. The decision by Washington to send 30,000 additional troops to Afghanistan has effectively made the war against the Taliban insurgency Mr Obama's war. By the end of this year, there will be more than 100,000 American soldiers on Afghan soil.
Even as preparations get under way to lay siege to Kandahar, the Taliban's political and spiritual stronghold, Mr Obama knows that no military force can succeed unless the Afghan government succeeds. Government corruption can neutralise or reverse any military gain on the ground. Indeed, it is one of the Taliban's chief recruiting tools. Washington isn't the only disgruntled party; Mr Karzai is unhappy, too. When US bombs kill Afghan civilians, it is he, not the American president, who suffers most politically. It is also Mr Karzai, not Mr Obama, who resides in the neighbourhood full-time - a fact that American officials clumsily minimised when they groused about his two recent meetings with their bête noire, the Iranian president Mahmoud Ahmadinejad.
Their mutual disappointment and incomprehension notwithstanding, Mr Obama has every right to awaken Mr Karzai to the desperate need for better, cleaner government. Both stand much to lose if the Afghan president fails. Most importantly, so do 28 million Afghans.