The Shiite Houthi rebels who descended from northern Yemen and sacked Sana’a late last year have scored a major victory, and in doing so signaled their intent to unite the country under their writ. Taiz, the country’s third-largest city, fell to the Houthis on Sunday. The victory marks another step towards the southern city of Aden, where deposed president Abed Rabbo Mansour Hadi has fled with the remnants of his government.

The fall of Taiz came as around 100 US commandos and support staff were pulled out of the al-Anad air base north of Aden over the weekend. The official word was that the troops were evacuated due to a ‘worsening security situation’ in the country; it probably had to do with the growing presence of al-Qaeda and ISIS militants in the area and no credible government presence to ensure the safety of the base. Al-Qaeda forces had overrun the nearby city of al-Houta just days before the decision to pull out dropped.

This leaves Washington without any frontline presence in a country that has featured prominently in President Obama’s drone-heavy counterterrorism strategy. Though drones can still operate from nearby bases in Africa and Saudi Arabia, a lack of intelligence-gathering and coordination from agents on the ground will hamper the effectiveness of the strikes, effectively creating a ‘blind spot’ that will reverberate not only in Washington’s ability to influence events on the ground but also its ability to track and pre-empt terrorist attacks within the United States.