The evacuation involved about 100 Special Operations forces members from the Al Anad airbase, sources in the region familiar with the situation told CNN. The State Department called it a temporary relocation.
Those evacuated, which include Navy SEALs and members of the Army's Delta Force, were the last American forces stationed in the Arab nation, which is home to al Qaeda in the Arabian Peninsula, the terrorist group also known as AQAP.
"We ... continue to actively monitor terrorist threats emanating from Yemen and have capabilities postured in the area to address them," State Department Spokesman Jeff Rathke said late Saturday. "As we have in the past, we will take action to disrupt continuing, imminent threats to the United States and our citizens."
"There is no military solution to Yemen's current crisis," Jeff Rathke said. "We urge the immediate cessation of all unilateral and offensive military actions."
The United Nations is taking the situation seriously. The Security Council will meet at 3 p.m. ET Sunday to discuss Yemen, the French mission said Saturday via Twitter.
For years, the U.S. military has worked closely with Yemen's government to go after AQAP, together carrying out numerous attacks like the 2011 drone strike that killed prominent al Qaeda figure Anwar al-Awlaki. And U.S. President Barack Obama has hailed this cooperation as a pillar in his anti-terrorism campaign.
"Yemen has never been a perfect democracy or a island of stability," Obama said in January, promoting the policy of "partnering and intelligence-sharing with that local government" as the best approach in a bad situation.
"The alternative would be for us to play whack-a-mole every time there is a terrorist actor inside of any given country," the President said.
But while there have been drone strikes as recently as last month
, these cooperative efforts have been hampered by Yemen's growing difficulty in maintaining unity and peace.
These include the rise of the Houthis, their battles with forces loyal to ousted President Abdu Rabu Mansour Hadi and the presence of not only al Qaeda fighters but other militants.
On Friday, for instance, ISIS purportedly claimed responsibility for bombings at two mosques in Sanaa what, if true, would mark that group's first large-scale attack in Yemen. The claim came in a statement posted on a site that previously carried ISIS proclamations, but couldn't be immediately authenticated by CNN.
Those blasts killed at least 137 people
and wounded 357 others, according to Yemen's state-run Saba news agency.
While ISIS and al Qaeda are both Sunni groups that espouse extreme versions of Islam and violent opposition to the West, that doesn't mean they will be working together anytime soon. In fact, AQAP strongly rebuked ISIS in a video
released in November, characterizing its leader Abu Bakr al-Baghdadi's declaration of an Islamic caliphate as illegitimate.
More than anything, the idea of the group calling itself the Islamic State violently flexing its muscles speaks to the chaotic situation there. With no one really in control, that means numerous groups -- including those with a history of killing civilians and lashing out at the West -- have been more room to operate and a better chance potentially to take over.
Deposed president: 'Houthis will not last'
Meanwhile, the main players for control of Yemen's government -- those siding with Hadi, who still claims to be president after being deposed earlier this year, and the Houthis, a minority group that's strongest in the northern part of the country -- remain very much at odds.
Just two days ago, a Yemeni jet commanded by the capital's Houthi conquerors fired missiles at a palace housing Hadi in the port city of Aden. No one was injured, but the direct strike nonetheless marked an escalation in the deadly fighting between the two sides.
The airstrikes came on the same day opposing Yemeni military forces -- some under the Houthis, others led by officers loyal to Hadi -- battled in Aden, said Aden Gov. AbdulAziz Hobtour. At least 13 people died and 21 others were injured in those clashes, according to Hobtour.
Hadi took to the airwaves of Adan TV, a station he recently started, on Saturday in his first televised speech since escaping house arrest.
He called on all political factions to take part in upcoming talks in the Saudi capital of Riyadh, condemning the Aden strike and urging Yemeni troops to refuse orders from Houthi officials. Hadi tied the Houthis to Iran, which he was said supported the "coup" that led to his departure from Aden.
"The Iranian agenda of the Houthis will not last," he said.
After Hadi spoke, the Houthi-run SABA news agency responded, saying the Supreme Revolutionary Committee has decided to mobilize forces and "directed security and military institutions to carry out their duties to confront (the) dirty war."
"The Committee announces the decision to call proud sons of the Yemeni people in all regions to unite, collaborate and cooperate with members of the armed and security forces in the face of terrorist forces in all parts of the country," the report said.
Mohammed Al Bukhaiti, a top member of the Houthi Political Council, said Hadi's speech won't help Yemen reach a peaceful resolution and accused him of reneging on a deal last September to transfer power.
"We blame Hadi for not implementing this deal that drew the road map that would have solved Yemen's ongoing crises," Al Bukhaiti said. "Hadi will be held responsible for the country's failures and that chaos that could follow."