CAIRO — With Yemen's president swept out of power by Shiite rebels, neighboring Saudi Arabia and allies such as Egypt are considering whether and how to intervene to stop a takeover of the country by rebels they believe are backed by Shiite Iran.
President Abed Rabbo Mansour Hadi has asked Gulf countries for military intervention and asked the United Nations to set up a no-fly zone to shut down rebel-held airports that he claims are being used to fly in Iranian weapons. The question is how Arab nations might act: Experts say a ground operation would be a likely impossibly daunting task, but that airstrikes are an option.
Gulf intervention would have been hard enough when Hadi was clinging to his authority after fleeing from the capital Sanaa to the southern port city of Aden. But it became an even tougher issue Wednesday, when Hadi was forced to flee Yemen by boat as rebel fighters — known as Houthis — and their allies advanced into Aden. The Houthis now control much of the north and a few southern provinces, backed by military forces loyal to Hadi's predecessor, longtime autocrat Ali Abdullah Saleh, who was removed in 2011 after a popular uprising.
There does remain resistance to the Houthis and Saleh — chiefly Sunni tribesmen in the north and center of the country, local militias and some units of the military and police remain loyal to Hadi, though they are profoundly weakened by his departure. The scattered nature of the opposition raises the question of whom would any foreign intervention being aiming to help. Also battling the Houthis are militants from al-Qaida's branch in Yemen, which has attracted some Sunni tribesmen as allies.
A summit of Arab leaders being held this weekend in Egypt is due to address a proposal to create a joint Arab defense force, an idea promoted by Saudi Arabia and Egypt to intervene in regional crises. Hadi is to attend the summit, being held in the Sinai resort of Sharm el-Sheikh. The summit is also likely to address the crisis in Yemen and how to deal with it — opening the door for a possible Arab League stamp of approval for action.
Egyptian Foreign Ministry spokesman Badr Abdellaty said that he and his Arab counterparts would discuss the idea of establishing a joint force on Thursday, to prepare for national leaders to decide on Saturday.
Gulf nations also have cited their own pretext for intervention. The Gulf Cooperation Council, made up of Saudi Arabia, Kuwait, Qatar, the United Arab Emirates, Oman and Bahrain, warned earlier this year that they would act to protect the Arabian Peninsula's security and described the Houthi takeover of parts of Yemen as a "terrorist" act. The Gulf's emergency military force, known as Peninsula Shield, intervened in Bahrain in 2011 to help the Sunni monarchy crush protests backed by the Shiite majority.
Saudi Arabia and its Gulf allies fear that the Shiite advance in Yemen is putting that strategic country on the southern Saudi borders into the control of Iran. The Houthis and Iran both deny Tehran is arming the rebels. Still, a direct air route recently opened from Tehran to Sanaa, which has been held by the Houthis since September, officially to being aid and medical supplies. Hadi and his allies say the heavy air traffic along the route is delivering Iranian weapons.
This week, Saudi Foreign Minister Saud al-Faisal warned that "if the Houthi coup does not end peacefully, we will take the necessary measures for this crisis to protect the region."
On Sunday night, Saudi Defense Minister Mohammed bin Salman visited troops in the south near the Yemen border. According to the state news agency he ordered the rapid completion of plans on building a naval base and new military camps in the area, apparently part of plans to build up the army presence in the area.
Egypt has said for months that it would act if the Houthis threaten vital shipping lanes that lead to its Suez Canal through the Gulf of Aden, an area the Houthis have already approached. Much of the Gulf region's oil exports destined for the West sail through the area.
But what would a military intervention look like? Not a ground invasion, says Sir John Jenkins, Middle East Executive Director for the International Institute for Strategic Studies.
"I think the likelihood of boots on the ground is very low," he said. "The Houthis are on home terrain, supported by Ali Abdullah Saleh, and have proved themselves effective fighters. They also have heavy weaponry and political support from Iran."
A ground invasion now would face the tough terrain between Saudi Arabia and Yemen, and a fierce enemy that for years beat back Yemeni government forces from its northern highland redoubts. Saudi Arabia intervened in Yemen against the Houthis once before, in late 2009 to early 2010, when the rebels' battle at the time with Saleh's regime spilled over across the border into the kingdom. Saudi Arabia retaliated with airstrikes against the Houthis and a ground incursion. The campaign left more than 130 Saudi troops killed.
More likely now would be airstrikes by some combination of Saudi Arabia, UAE or Bahrain, all of which have advanced versions of American F-16s, or Egypt, which has large numbers of older versions. Egypt would have to send its planes to air bases in Saudi for the raids, and other countries would likely opt to do the same.
Saudi Arabia could also step up its arming of Sunni tribesmen against the Houthis. The kingdom already funds and arms Sunnis in Yemen's Marib province, which borders the kingdom.
But with Hadi driven out, there isn't a clear front line for international intervention to support. Any intervention would likely be in the name of restoring Hadi — but doing so with airstrikes alone would be a difficult task.
"Air strikes are a possibility, against military targets, particularly Houthi air assets, artillery and tanks, but that brings its own risks," Jenkins said. "At the moment preserving the integrity of the land border with Saudi Arabia and the key passages in the Red Sea seems to me the priority."
Follow Brian Rohan on Twitter at www.twitter.com/brian_rohan