KABUL, Afghanistan -- One evening last August, as President Hamid Karzai wrapped up an official visit to Iran, his personal plane sat on the airport tarmac, waiting for a late-running passenger: Iran's ambassador to Afghanistan. The ambassador, Feda Hussein Maliki, finally appeared, taking a seat next to Umar Daudzai, Karzai's chief of staff and his most trusted confidant. According to an Afghan official on the plane, Maliki handed Daudzai a large plastic bag bulging with packets of euro bills. A second Afghan official confirmed that Daudzai carried home a large bag of cash. "This is the Iranian money," said an...