What's Going On in Yemen

— -- The failed missile attack on an American warship off the coast of Yemen highlights the chaotic situation in that country where a Saudi-led coalition has intervened militarily against the Iranian-backed Houthi militia group that seized power in early 2015.

The Pentagon believes that two missiles fired Sunday at the guided-missile destroyer USS Mason (DDG 87) in the southern Red Sea came from Houthi-controlled territory in Yemen. Last weekend, a ship from the United Arab Emirates suffered extensive damage in another missile attack believed to have also come from Houthi militants.

In the wake of that attack, the Mason and two other U.S. Navy ships were sent to the waters off Yemen to essentially dissuade any attacks on civilian shipping.

Meanwhile, American support for the Saudi-led coalition’s military intervention against the Houthis is fraying following an airstrike Saturday on a funeral hall that may have killed more than 100 civilians. A White House statement said it was “deeply disturbed” by the airstrike and warned that support for the Saudi coalition “is not a blank check.” The airstrike is the latest in a series of incidents that have raised the Obama administration’s concerns about how the fight against the Houthis is being waged.

ABC News looks at the situation in Yemen and what this weekend’s events could mean for the U.S. role in Yemen:

Who Is Fighting in Yemen?

In January 2015, a Shiite militant tribal group known as the Houthis seized power from President Abdrabbuh Mansour Hadi, who was forced to resign. A civil war developed as the Houthis fought against pro-government forces in southern Yemen. In February 2015, as the violence spiraled out of control in Yemen the United States suspended operations at its embassy and evacuated 100 military advisers that had been supporting the Yemeni government’s fight against al-Qaeda in the Arabian Peninsula.

A short time later Saudi Arabia and other Gulf nations intervened militarily in Yemen against the Houthis to restore Hadi to power and check Iranian military support for the Houthis. The United States quietly began supporting the Saudi-led coalition by providing it with intelligence, weapons sales and air-refueling support.

Since then, coalition troops have held back the Houthi advance on southern Yemen, but the Houthis remain in control of the capital city of Yemen and much of the western part of the country.

The United States has scaled back its support for the Saudi coalition as it has waged an airstrike campaign that by some estimates has led to 2,000 civilian deaths. Recently, the U.S. had one military adviser working with the coalition in its military planning in Yemen and has relocated to Bahrain the 45 personnel that had been doing that work at a military base in Saudi Arabia.

This weekend, the White House warned that its support for the coalition was “not a blank check” after it raised concerns about a coalition airstrike that killed than 100 civilians attending a funeral in the capital city of Sanaa.

Meanwhile, al-Qaeda in the Arabian Peninsula (AQAP) has taken advantage of the power vacuum in Yemen to rebuild its operations. Though U.S. military advisers were pulled from Yemen, the U.S. military continues launching drone attacks against AQAP from a base in nearby Djibouti.

Why Is Yemen Important

Yemen is an impoverished country on the southwestern tip of the Arabian Peninsula next to Bab-el-Mandeb, a narrow strait separating Yemen and the Horn of Africa that joins the Red Sea and the Indian Ocean.

The U.S. has a strong interest in ensuring the safety of commercial shipping and the 3-to-4 million barrels of oil that travel through the vital waterway each day.

U.S. Navy ships have often been deployed to the waters off Yemen to prevent a military or terrorist threat to the key shipping lane.

A stable government in Yemen is important to Gulf countries wary of Iran’s military support and influence with the Houthis. Gulf countries fear the relationship could lead to an Iranian military presence in the Arabian Peninsula, a concern that would exacerbate the already tense relationship with Iran because of the threat its nuclear program has posed to the region.

Yemen is also the home to al-Qaeda in the Arabian Peninsula, the most dangerous al-Qaeda affiliate, which is committed to taking over control of Yemen and carrying out terror attacks against the United States and other western countries. A security vacuum in Yemen gives AQAP the safe haven it needs from which to plot overseas terror attacks.

AQAP also remains the major terrorist threat to Saudi Arabia and other Gulf countries.

A Houthi Threat to the United States?

Last weekend, an Emirati military transport ship was severely damaged by Houthi militants who fired missiles at the vessel while it was in international waters. The United Arab Emirates has been a key member of the coalition in Yemen and has provided ground troops, aircraft and warships in the fight against the Houthis.

The U.S. Navy quickly deployed three ships near Bab-el-Mandeb to ensure there was no threat to international shipping. They included the destroyers USS Mason and USS Nitze as well as the USS Ponce, an afloat forward staging area that normally houses special operations forces.

On Sunday, the Pentagon announced that two missiles had been fired at the USS Mason from Houthi-controlled territory in Yemen. The missiles fell in the water short of the ship, but the threat was so great that the ship’s crew deployed defensive measures to counter the incoming missiles. It is the first known attack by the Houthis on an American warship.

That same day, the Houthis fired a long-range missile at Saudi Arabia targeting the King Fahd military base outside of Taif, though there was apparently no damage to the base.

Both incidents may have been in retaliation for the deadly airstrike on the funeral, though the Houthis have denied that they fired missiles at the USS Mason.

The incidents also highlight the long-range missile threat the Houthis can pose to neighboring countries and U.S. warships in the waters off Yemen. It is unknown if the missiles were Soviet-era missiles they took over from government forces or if they were new missiles that Saudi Arabia claims have been provided by Iran to the Houthis.