To be sure, more US troops on the ground isn’t a silver bullet. There also needs to be an improvement in both the Afghan security forces and the quality of governance. But more troops are a necessary if not sufficient condition for progress. Only with more manpower can the US hope to be able to protect the main population centers.
The White House’s wariness to send more troops to Afghanistan so soon after the latest increase is understandable. But having entrusted McChrystal with the mission—a mission that Obama has repeatedly described as central to the war on terror, the commanded on the ground should be given the tools he feels he needs.