The U.S. airlifted all "non-emergency" personnel from Yemen on Tuesday, just hours after it was revealed that an American drone strike killed at least four suspected al-Qaeda militants in the same country. The British government also followed suit, withdrawing all of its diplomatic personnel from their embassy in Saana overnight. The State Department also instructed any U.S. citizens in Yemen to leave the country "immediately."
The decision comes days after the United States issued a globe travel warning and closed 19 embassies in the Middle East and Africa due to an unspecified security threat. On Monday, sources revealed that intelligence agencies had intercepted communications from al-Qaeda's top leader, Ayman al-Zawahri, and Nasser al-Wuhayshi, his counterpart in Yemen, in which Zawahri apparently ordered a terrorist attack to be carried out from Yemen. The fact that two such highly placed operatives were talking directly seems to have escalated the seriousness of the threat.
There is also some concern that the recent rash of prison breaks in Pakistan, Iraq, Libya, and elsewhere may be part of a coordinated effort to recruit new militants and rescue old ones ahead of some larger terrorist operation. (There have been at least nine such prison breaks targeting suspected terrorist inmates in the last month alone.) Officials are also expecting a rise in activity in the final days of the holy month of Ramadan, which concludes this week.