In this image provided by the U.S. Army, contactors from General Atomics load hellfire missiles onto an MQ-1C Gray Eagle at Camp Taji, Iraq. [AP]
For a year, U.S. officials have been saying that taking out a terrorist threat in Afghanistan with no American troops on the ground would be difficult but not impossible. Last weekend, the U.S. did just that - killing al-Qaida leader Ayman al-Zawahri with a CIA drone strike.