In 2015, the United States closed its embassy in Yemen as a civil war tore the country apart. The U.S. Marines guarding the embassy had to ditch some of their weapons before boarding a chartered commercial airliner with embassy staff as Iranian-backed forces stormed the capital city of Sanaa and helped themselves to abandoned embassy vehicles as well as the compound itself.

US special operations forces who had been hunting Al-Qaeda in Yemen were also withdrawn when the Iranian-backed group known as the Houthis seized the capital.

But despite the forced departures, the American military now finds itself increasingly involved in Yemen's civil war - and there are fears it could be open-ended.

In October, the Houthis fired two missiles at a pair of U.S. Navy warships in the Red Sea. Neither missile hit its target after the guided-missile destroyer USS Mason launched three missiles of its own to intercept the incoming Houthi missiles. It is believed to be the first time a Navy warship fired interceptor missiles to defend itself during a missile attack.

Days later, the U.S. Navy retaliated by launching Tomahawk cruise missile from USS Nitze--destroying three Houthi coastal radar sites in Yemen that the Pentagon said were used to attack the American warships.

The United States is supporting a Saudi Arabia-led coalition fighting the Houthis.

But for some, the biggest threat to the United States remains Al Qaeda’s Yemen branch.

The forced American withdrawal from Yemen slowed the fight against Al Qaeda in the Arabian Peninsula or AQAP, according to American officials at the time.

“That is probably one of the most lethal branches of Al Qaeda and it has proven itself to have these ambitions to attack our country,” said Stephen Seche, the U.S. ambassador to Yemen from 2007-2010.

“They have a bomb maker name Ibrahim Nasiri who is very, very focused on trying to get these non-metallic, non-ferrous explosives that can evade all our detection equipment. That's a serious risk and a serious concern for me and everybody concerned about national security.”

In 2009, AQAP sent Umar Farouk Abdulmutallab, now known as the Underwear bomber, aboard an airliner headed to Detroit with the aim of detonating his explosives and killing everyone aboard. The explosives never went off and he was arrested at the airport.

In 2011, a U.S. drone killed the radical American-born Muslim cleric Anwar Al Awaki, who had been directing and planning attacks on the U.S. It was the first U.S. drone strike on a U.S. citizen. Weeks later, his son was also killed in a drone strike.

Since President Trump has taken office, airstrikes against Al Qaeda in Yemen have more than doubled compared to the past five years. There have been more than 80 this year.

U.S. military actions in Yemen also have increased.

U.S. special operations forces have returned in small numbers. In two ground raids, one U.S. Navy SEAL, Ryan Owens, was killed days after President Trump took office.

All this comes as the civil war, which many see as a proxy fight between Saudi Arabia and Iran, rages inside Yemen, killing thousands of civilians.

The Saudis launched the surprise war against the Houthis almost two years ago. The Saudi and Emerati coalition has been accused of carpet bombing residential areas and war crimes.

Some fear the United States is getting sucked into another fight without end.

“The way we're dealing with failed states in the Middle East is on a ‘whack-a-mole’ kind of approach which means we kind of deal with the crisis of the moment,” said former defense secretary and CIA director Leon Panetta in an interview with Fox News.

Panetta worries the U.S. may be bowing too much to pressure from Saudi Arabia to get further involved militarily in Yemen in what is looking more like a proxy war against Iran and the Houthis they are backing.

“The Obama administration frankly did not pay enough attention to Iran's support to terrorism in that region particularly at the time they were negotiating with the Iranians,” said Panetta. “I think it's very important for President Trump not to simply bounce to the other extreme.”

The former U.S. ambassador, who left Yemen at the start of the Arab Spring in 2010,had this warning:

“There is a proclivity to stumble into these wars, into these conflicts if you will and I think that's the danger,” Seche said. “This is a low level conflict that then grows and our interest and our involvement in it grows and it almost sneaks up behind you until you realize that you are knee deep in the muck, and it's very hard to extricate yourself at that point.”