After clashes in Yemen expanded into a regional conflict, Egypt threw its lot in with Saudi Arabia and other Sunni countries. They are working to counter the advance of Shiite Houthi militias.

The Houthis are backed by Iran. In recent months, they’ve overthrown Yemen’s Sunni government and gained control over several cities and regions of the country. By solidifying control of Yemen, Iran could advance both its general goal of regional hegemony, and its specific goal of controlling the Red Sea.

Egypt—like Saudi Arabia and other Sunni states—fears Iran’s growing power. It wishes to prevent Tehran from obtaining its expansionist goals. Egypt is also committed to maintaining its control over the Suez Canal, which it fears could be at risk. “If the Houthis, who are believed to be backed by Iran, win, it means that Iran will get control over the Red Sea,” Saeed Sadek, a Cairo-based professor of sociology, told al-Arabiya News. “Egypt and Saudi Arabia will not allow this to happen,” he added.

Saudi Arabia is leading the campaign to push back at the Houthis and Iran. Besides Egypt, the campaign also includes the other Gulf Cooperation Council (gcc) states, as well as Jordan, Sudan, Morocco and Pakistan. Turkey and the United States also back the movement. So far, Egypt’s role has been limited to air and naval support, but Cairo has said it is also prepared to deploy troops in the event of a ground operation.

Some analysts believe such a ground operation in Yemen would weaken Egypt and possibly lead to unrest in Cairo.

On March 26, the Brookings Institution, a think tank based in Washington, D.C., explained this view: “Even with U.S. assistance, the gcc and its coalition partners lack the capacity to break Houthi ground operations the way that American air power has been able to smash [the Islamic State] ground operations in Iraq and Syria.”

Brookings called Cairo’s willingness to deploy ground troops “curious” in light of Egypt’s unsuccessful participation in the Yemeni civil war of 1961-1967. “The Egyptians are not likely to improve the chances of success, and Egypt is also a fragile state struggling to deal with enormous domestic political and economic problems. It does not need a potentially debilitating and divisive foray into Yemen ….”

Brookings says Saudi Arabia, too, could suffer destabilization if it expands its intervention in Yemen: “The kingdom lacks the military capacity to intervene decisively in Yemen, and if it tries by sending in large numbers of ground troops, the most likely outcome would be a debilitating stalemate that will drain Saudi military resources, financial reserves, and political will.”

Also relevant is the question of how long the U.S. will continue supporting the anti-Houthi campaign. The Obama administration’s track record suggests that America could withdrawal its backing from the campaign in part or whole at any time. If U.S. backing were removed, the drain on the Egyptians and Saudis would be potentially far greater.

If the Yemen conflict drags on, and Egypt and Saudi Arabia become further embroiled in it, one or both powers could emerge considerably weaker. This would represent a success for Iran: If two of the Middle East’s primary forces opposing Tehran weaken, Iran’s comparative power in the region would be greater.

A weakened and exasperated Egypt could also work to Iran’s advantage by ultimately aligning Cairo with Tehran. After Egypt’s 2011 revolution toppled the military dictatorship of Hosni Mubarak, the country became an Islamist state. While Mubarak’s Egypt had viewed Iran as an archenemy, the new Islamist Egypt—led by the Muslim Brotherhood (MB)—positioned itself as Iran’s most powerful regional ally. Iran considered Egypt’s 2011 revolution an “Islamic awakening,” and viewed it as a major victory for Iran.

But then came the counterrevolution.

Many in Egypt’s powerful military didn’t like being governed by the Muslim Brotherhood and President Mohamed Morsi. Millions of Egyptian civilians were also unhappy with Morsi’s leadership. In July 2013, the military staged a coup that removed Morsi from office, paving the way for the chief of the armed forces, Abdel Fattah al-Sisi, to become Egypt’s ruler.

In many ways, Sisi returned Egypt to what it had been under Mubarak. He led a fierce crackdown on Islamists, executing hundreds of MB members and branding it an illegal terrorist group. He injected new zeal and power into the military establishment, returning the nation to military rule. And he quickly cooled Egypt’s camaraderie with Iran, a move that Tehran openly criticized.

That brings us back to the present. Sisi’s Egypt is closer to Saudi Arabia—Iran’s nemesis—than it has been in decades. Cairo is accepting billions of dollars in Saudi aid, and is actively working with the Saudis to suppress Iran’s Houthi proxies in Yemen.

Internally, however, Egypt is anything but stable. Rates of poverty and unemployment are soaring, corruption remains rampant and some Islamists wonder why Morsi—the only person the people of Egypt managed to elect as ruler in their 4,000 years of history—had to go. Although most subversive groups have been marginalized or extinguished, many revolutionaries remain. And they are dissatisfied with the status quo. If Sisi continues focusing on Yemen, and investing Egypt’s precious resources into a potentially protracted conflict, it could be enough to reignite protests. If such protests were to bring about another regime change, the new ruler would likely bear more resemblance to Morsi than to Sisi.

The Yemen conflict could die down, or it could continue expanding into an ever larger regional battle, possibly kicking off a war between the Middle East’s two main blocs. If the latter happens, and if Egypt increases its intervention in the turmoil, it could bring Egypt alongside Iran. To understand why such an outcome would be significant, read “Iran-Egypt Alliance Prophesied.”