SANAA — Ambiguity continues to shroud the extent of Egypt's involvement in the Saudi-led coalition"s fight against rebel forces in Yemen.

The 10-member coalition has recently stepped up its campaign against the Iran-backed Houthi rebels, who control the capital of Sanaa. Forces have moved on from a months-long phase of extensive airstrikes that flattened the insurgency's military holdouts — and inflicted grave civilian casualties — to a ground invasion, in which coalition troops are attempting to force Houthis back. Now the coalition is trying to battle an increasingly powerful al-Qaeda presence in Yemen too.

The number of Egyptian soldiers on the ground and the scope of their participation in the new operation remain unclear. The Egyptian government has yet to make an official announcement on the matter, but on Aug. 1 the National Defense Council (NDC) agreed to extend military involvement in Yemen by another six months.

But given difficult fighting conditions, the added layer of complexity wrought by the humanitarian crisis now strangling Yemen, and a nightmarish history of Egyptian intervention there, what would motivate Egypt to stay involved in what is effectively a decades-old power struggle between Saudi Arabia, Yemen and Iran?

"No comment" on deployment

When Egypt first signed on to the initial Operation Decisive Storm, President Abdel Fattah al-Sisi stressed that the country was only participating with naval and air forces. "An announcement will be made if any other forces are deployed in the operation," he said during an April speech at the Military Academy.

So far, according to state media, Egypt has contributed air forces and four naval vessels to the coalition to help tighten the siege on Yemen, and apparently also to prevent Iranian supplies from reaching the Houthi movement. Egypt has also joined airstrikes targeting Houthi positions.

But an associate of former President Ali Abdullah Saleh, who was ousted in Yemen's 2011 uprising, recently said that Egypt is now deploying some 3,000 ground troops to Al-Makha, which overlooks the strategic Bab-el-Mandeb area, with the aim of securing Red Sea traffic. Local media have reported the same in recent weeks, though it hasn't been possible to verfity their accuracy.

A leading journalist from the southern Yemeni port of Mukalla, who spoke to Mada Masr on condition of anonymity, says that there are ongoing negotiations, including with the Emiratis, to compel al-Qaeda to leave Mukalla, which it seized in April, without bloodshed. But the journalist says he doesn't know any details regarding the deployment of coalition forces.

"Egypt has participated in the coalition from the beginning with air and naval forces," says Brigadier General Ahmed Asiri, coalition spokesperson. "Until now, the Egyptian political leadership has not made an announcement for the deployment of Egyptian ground troops."

When asked if Egypt has promised to send ground troops, he says, "I can't comment on this until the Egyptian leadership makes an announcement."

Why would Egypt intervene?

The Yemen conflict has often been read as a proxy war between Saudi Arabia and Iran, but Egypt has little interest in that rivalry. Instead, an Egyptian intervention is arguably tied to the billions of petrodollars that Saudi has given the government since former President Mohamed Morsi's 2013 ouster.

Sisi's announcement that the National Defense Council was extending the mission of Egyptian troops came just two days after Saudi Deputy Crown Prince Mohamed bin Salman al-Saud visited Cairo.

Saudi Arabia and Egypt recently sealed the so-called "Cairo Declaration" to enhance bilateral relations, promising to reject "any attempt to interfere in the Arab countries' internal affairs." The Cairo Declaration also included a package of measures to develop military cooperation, and to work on setting up a joint Arab military force.

Egypt has been leading efforts to build this force in response to a regional breakdown of central governments and the simultaneous rise of Islamist militants. In addition to the campaign in Yemen, Libya has acted as laboratory for the joint mission.

Prince Mohamed's visit may have been an attempt to solidify relations after reports of a deep split between Egyptian and Saudi leadership over their positions on the Muslim Brotherhood.

The Saudis are striking an alliance with the Islah Party, Yemen's Muslim Brotherhood branch, while Egypt is cracking down on the group, killing and imprisoning thousands of members. Several high-profile Brotherhood members have been sentenced to death — including the ex-president — on charges stemming from the violence that has struck Egypt since Morsi's ouster.

The deployment rumors also come shortly after Yemen's exiled President Abd Rubbuh Mansur Hadi visited Egypt for the inauguration of the Suez Canal extension. His spokesman told reporters that Hadi "praised" Egypt's "decisive and supportive" role in restoring legitimacy in Yemen.

Aside from strengthening an economically strategic friendship with Saudi, the potential Egyptian deployment might reflect Sisi's fear of a Houthi backlash that could undermine the security of the strategic Bab-el-Mandeb entrance to the Red Sea, and hence control of Suez Canal traffic. Sisi has stressed on more than one occasion that the security of Bab-el-Mandeb is a "red line."

But Houthi officials say that they have given assurances to Cairo that they wouldn't take any action that could harm Egypt's interests. They accuse Hadi's exiled government and the Saudis of fanning Egyptian fears of a Houthi threat.

"The Saudi leadership is trying to freak Egyptians out by telling them Ansar Allah intends to close Bab-el-Mandeb," says Daif Allah al-Shami, a member of the Houthi political bureau. "The Gulf is pressing Egypt to send forces, and we had hoped that the Egyptians wouldn't submit to these pressures."

"If Egypt sends troops to Yemen," he warns, "this will be a dark spot in the history of the Egyptian army. They will be invading Yemen, just like they did before."

A daunting history

If their participation in the war is confirmed, Egyptian troops would face an arduous mission in Yemen's mountainous terrain. Whether confronting Houthis or al-Qaeda militants, Egyptians would be battling die-hard fighters hardened by decades of guerrilla warfare.

"There's a big difference between today's war and yesterday's story," says retired Gen. Hossam Sweilam. But many observers believe current events evoke Egypt's military intervention in Yemen in the 1960s.

At the time, Egypt's United Arab Republic with Syria had unraveled, and then-President Gamal Abdel Nasser threw his weight behind Yemeni republicans staging a coup against the country's aging imamate, which Saudi Arabia supported.

Thus began a protracted war for which scholars say Egypt was completely unprepared, to the extent that Egyptians didn't even have topographic maps of Yemen. By the war's end in 1967, historians estimate that Egypt had sent 70,000 troops to Yemen, losing 26,000 in the process.

A post-2011 meltdown

The current conflict might bring back memories of Egypt's last military foray in Yemen, but the latest operations are the result of both recent and deep historical rivalries that have little to do with Egypt.

The oil-rich kingdom of Saudi Arabia has long treated Yemen as its backyard, funneling billions of dollars into the pockets of Yemeni tribal, military and political leaders for decades to ensure their unbreakable loyalty.

After the 2011 uprising that eventually toppled longtime autocrat Saleh, Saudi Arabia and the Gulf Cooperation Council (with UN and U.S. support) struck a deal that gave Saleh immunity from prosecution in return for relinquishing power. The deal split power between Saleh's party and the opposition.

For many of the Yemenis who staged the anti-Saleh uprising, this deal paved the way for the current conflict, since it left the centers of power — Saleh and the Islah Party — untouched, while keeping the rebel movement that had been part of the uprising out of the political equation.

Critics say that Islah worked to integrate its members in all government institutions and army units, and that the post-revolution president, Hadi, succumbed to Islah pressure.

Part of the GCC deal was to purge Yemen's armed forces of Saleh loyalists and family members. This shakeup, alongside growing Islah influence, left Saleh searching for new allies outside the transitional power structure.

Those new allies were the Houthis.

While both the Houthis and Saleh deny any alliance, developments on the ground have shown otherwise.

Allying with disenchanted tribes in the north, the Houthi group fought its way from its heartland in Saada down to the capital, defeating tribes allied with Islah along the way.

In September 2014, Houthis took over the capital. A few months later, they placed Hadi and members of his government under house arrest. In March 2015, Hadi fled to Aden, then to Saudi Arabia, pleading for a military intervention to roll the Houthis back.

Abdullah al-Rahbi, a senior employee in the Yemeni president's office, recalls a widely echoed saying that sums up Yemen-Saudi relations. "On his deathbed, the founder of Saudi Arabia left a will for his grandchildren: "Saudi's well-being is in Yemen's ill-being, and Yemen's well-being is in Saudi's ill-being.""

Other historical clashes have also fueled the resentment.

On to al-Qaeda

The Saudi-led coalition has come under criticism for turning a blind eye to al-Qaeda's recent gains in Yemen, and is now setting its sights on the extremist group. At the same time, al-Qaeda is reportedly negotiating a withdrawal from Mukalla after handing power to a civilian council.

Al-Qaeda forces first entered Mukalla on April 2, 2015, when they took control of several army barracks, the central bank and the prison. The militants freed more than 300 inmates, including their notorious leader Khaled Baterfi.

In a new video released by al-Qaeda in Yemen, a commander says it is fighting on all fronts in Yemen, and that Mukalla was seized as a preemptive measure before the Houthis could capture it.

The group has since struck a power-sharing deal that ostensibly gives a civilian council power to administer city affairs, while the militants police the streets alongside local tribesman. According to the deal, al-Qaeda would eventually withdraw from the city when the council is powerful enough to secure it from the Houthis.

Over the past months, many of the group's top leaders were killed in a series of U.S. drone strikes in Mukalla. The strikes have dampened the group's morale but hardly hindered it from expanding.

In fact, critics say that the coalition's efforts have indirectly been helping al-Qaeda, as weapons airdropped to anti-Houthi forces have ended up in the hands of the extremist group. Moreover, liberated areas in Aden and elsewhere have been left with a profound power and security vacuum — and al-Qaeda is the only group organized enough to fill it.

Yemen sinks into catastrophe

So far, the Saudi-led coalition's airstrikes on Yemen have decimated military holdouts, weapon depots and the homes of rebel leadership. A recent ground incursion led by UAE and Saudi forces helped recapture the southern city of Aden and several other cities in the south.

As the military tide shifts in favor of the coalition, Houthis have held peace talks with the UN Envoy to Yemen. They reportedly discussed a ceasefire, the deployment of a peacekeeping force and the implementation of the Security Council resolution stipulating the withdrawal of armed groups from all cities.

But the potential overture might be too late for Yemen. Since the coalition's offensive began March 26, more than 4,000 civilians have died and more than 19,000 wounded and more than 1 million displaced, according to the International Committee of The Red Cross. Andt least 1,000 children have been killed or injured.

The violence has pushed the already impoverished nation to the brink, and devastated its infrastructure.

"We are witness to a humanitarian catastrophe in Yemen," the UN Office for the Coordination of Humanitarian Affairs recently said in a statement.

The World Food Program is warning of famine, saying that the total number of people without enough access to food has surged to 13 million, the group's director Ertharin Cousin said during a recent briefing.

"Right now, the conflict-driver convergence between the lack of staple food, access to clean water and a diminished fuel supply create the dawn of a perfect storm for the most vulnerable Yemeni people."