WASHINGTON — They are the Sopranos of the Afghanistan war, a ruthless crime family that built an empire out of kidnapping, extortion, smuggling, even trucking. They have trafficked in precious gems, stolen lumber and demanded protection money from businesses building roads and schools with American reconstruction funds. They safeguard their mountainous turf by planting deadly roadside bombs and shelling remote American military bases. And they are accused by American officials of being guns for hire: a proxy force used by the Pakistani intelligence service to carry out grisly, high-profile attacks in Kabul and throughout the country. Today, American intelligence and...