Commentary With our political and military establishment spending twenty years waging war in the mountains of central Asia, Americans now know that the old saying about Afghanistan and imperial ambition is a lie. A great nation with a keen pride in its own identity and the destiny defined by it doesn’t risk blood and treasure to convince primitive tribes to adopt its style of governance. Only a failing power that has lost all sense of what once made rivals shrink would spend the lives of its young men and women to plant its flag on a pile of inconsequential rocks. Afghanistan is not the graveyard of empires. Rather, it is where failing regimes go to be euthanized. The Soviet Union was already crumbling when Leonid Brezhnev sent troops to prop up a Communist regime in 1979. Months after Mikhail Gorbachev withdrew the last Soviet soldier in February 1989, the Berlin …