In early May it was revealed that American Special Forces troops had recently returned to Yemen and had played a role in the recent UAE (United Arab Republic) led offensive that drove al Qaeda out of the major port of Mukulla on the southern coast. American special operations forces had left Yemen in early 2015 when the Shia rebels captured al Anad airbase, the largest airbase in the country and where American UAVs and special operations troops were stationed. It was known that the U.S. continued using armed UAVs based across the Gulf of Aden, in Djibouti, for flying recon missions over Yemen. The UAVs, with an endurance of 15-20 hours (depending on how many missiles carried), and requiring about two hours travel time to Yemen and back. These UAVs continued to monitor the situation and when the Saudi led Arab coalition entered the Yemen civil war in early 2015 (in part because of the loss of al Anad) American UAV support was a useful asset.
Since 2009 the American JSOC (Joint Special Operations Command) have been expanding its fleet of UAVs in Djibouti so there was no problem replacing the UAV coverage after the loss of al Anad. After American UAVs left Yemen in early 2015 some were apparently moved to the UAE where they continued to support UAE and other Arab forces in Yemen. American intelligence and aerial refueling aircraft also supported Arab warplanes operating over Yemen.
The American special operations effort in Yemen had been expanding since 2012 when the U.S. brought more intelligence and security specialists to assist and train their Yemeni counterparts. Most American counter-terrorism assistance is still performed by U.S. forces stationed outside the country (in Saudi Arabia, other Gulf States, Djibouti across the Straits of Aden and off shore on U.S. Navy ships).
In 2010 Yemen allowed the United States to establish a local intelligence operation. This had actually been going on for over a decade, but in very limited form. But after 2010 American UAVs and electronic reconnaissance aircraft are more frequently seen in Yemen, along with CIA and U.S. Army Special Forces operatives (the former for setting up informant networks, the latter to help with that and to train Yemeni special operations troops.) The Yemeni government described American UAV missile attacks as Yemeni Air Force operations. At the same time some 200 U.S. Army Special Forces troops, with lots of experience fighting tribesmen in mountains) and intelligence (via UAVs and electronic eavesdropping) have been making themselves useful. It’s the American intelligence effort that has enabled the government to stage raids and bombing attacks on concentrations of rebels and Islamic terrorists. All that was removed from the country when the Shia rebels in the north moved south in 2014 and, with assistance from the recently (in 2012) deposed president aid from Iran, occupied the Yemeni capital. Now the Shia rebels are on the brink of defeat and the Islamic terrorists who thrived during two years of civil war are under heavy attack.