One of the major casualties of the current civil war in Yemen is the American effort to find and kill key al Qaeda personnel. This effort loses a lot because many Yemeni intelligence units were shut down. Looters grabbed some of the secret files (or intelligence personnel took and sold data to the Islamic terrorists). Not only was much of the Yemeni informant network shut down but the Islamic terrorists found out who some key informants were and shut them down (via killing them or chasing them away). Some of the Yemeni intelligence units sided with the Shia rebels who have a close relationship with Iran. The damage here was not as bad as it could be. Iran also wants these Sunni Islamic terrorists dead, but the Americans had the missile armed UAVs to do the job while the Iranians don’t. Now that the Sunni Arab neighbors of Yemen have intervened there is guaranteed to be months of chaos, the kind of environment Islamic terrorists thrive in.
The U.S. also lost the use of a Yemeni air base, where American ground crews to maintain UAVs and provide emergency landing facilities for UAVs based elsewhere in the region. The United States also had over a hundred Special Forces and intel troops in Yemen to help train their Yemeni counterparts and assist in running counter-terror operations.