From Newsweek:

Reading about the struggles for national liberation in Indochina from the 1950s through the Vietnam War, McChrystal became fascinated by the challenges of counterinsurgency. He learned that putting down a guerrilla movement was impossible without winning the support of the local population. His convictions were reinforced by his experience running black ops in Iraq and Afghanistan. Counterter-ror operations—hunting down HVTs—went hand in hand with effective counterinsurgency, with winning over the local population. Indeed, he came to believe, “you can’t have one without the other.” To successfully find and kill terrorists requires the intelligence and cooperation that only the locals can provide. McChrystal already had this mindset before Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, pushed him forward to replace Gen. David McKiernan as head of Coalition forces in Afghanistan.