The lesson is simple: Clear purpose creates a united America, and a united America wins wars. Our presence in Afghanistan has lacked this clear purpose for many years. Unfortunately, this fact went unnoticed by many because of a strange new truth about how America fights wars — we don’t use nearly the same number of troops as we did in years past. This is good news on the surface — we are far from the deployment levels of World War II or even Korea and Vietnam, and that means we are risking fewer lives. But reduced troop deployment means we are more detached from these wars than ever before, which is precisely what has made them endless. With so few in the field, most probably don’t have a son or daughter in Afghanistan, and probably don’t know someone down the street nervously watching the news for signs of violent battle in the desert that may have taken American lives.