Mr. Obama concluded in his first year that the Bush-era dream of remaking Afghanistan was a fantasy, and that the far greater threat to the United States was an unstable, nuclear-armed Pakistan.

When President Obama joins other NATO leaders Sunday and Monday, the full extent of how his Afghan strategy has changed - from "war of necessity" to withdrawal on his terms - will be apparent.

From The New York Times:

Mr. Obama concluded in his first year that the Bush-era dream of remaking Afghanistan was a fantasy, and that the far greater threat to the United States was an unstable, nuclear-armed Pakistan. So he narrowed the goals in Afghanistan, and narrowed them again, until he could make the case that America had achieved limited objectives in a war that was, in any traditional sense, unwinnable.
       

“Just think how big a reversal of approach this was in just two years,” one official involved in the administration debates on Afghanistan said. “We started with what everyone thought was a pragmatic vision but, at its core, was a plan for changing the way Afghanistan is wired. We ended up thinking about how to do as little wiring as possible.”
      

The lessons Mr. Obama has learned in Afghanistan have been crucial to shaping his presidency. Fatigue and frustration with the war have defined the strategies his administration has adopted to guide how America intervenes in the world’s messiest conflicts. Out of the experience emerged Mr. Obama’s “light footprint” strategy, in which the United States strikes from a distance but does not engage in years-long, enervating occupations. That doctrine shaped the president’s thinking about how to deal with the challenges that followed — Libya, Syria and a nuclear Iran.

In interviews over the past 18 months, Mr. Obama’s top national security aides described the evolution of the president’s views on Afghanistan as a result of three rude discoveries.

Mr. Obama began to question why Americans were dying to prop up a leader, President Hamid Karzai of Afghanistan, who was volatile, unreliable and willing to manipulate the ballot box. Faced with an economic crisis at home and a fiscal crisis that Mr. Obama knew would eventually require deep limits on Pentagon spending, he was also shocked, they said, by what the war’s cost would be if the generals’ counterinsurgency plan were left on autopilot — $1 trillion over 10 years. And the more he delved into what it would take to truly change Afghan society, the more he concluded that the task was so overwhelming that it would make little difference whether a large American and NATO force remained for 2 more years, 5 more years or 10 more years.