With regimes collapsing throughout the Middle East, many Washington experts wonder if two U.S.-aligned monarchies, Bahrain and Jordan, might be the next possible candidates for the type of regime change seen of late in Tunisia and Egypt. In recent weeks, thousands have demonstrated in Bahrain in favor of overthrowing the monarchy after security forces killed several protesters calling for constitutional reforms and investigations into government corruption and human rights abuses. In Jordan, meanwhile, demonstrations against rising food prices and rampant unemployment quickly transformed into pro-democracy rallies, rocking the Hashemite Kingdom to its core.

The stakes for the U.S. are enormous. The overthrow of either regime would threaten American interests and further destabilize the already-volatile region. Bahrain’s strategic position in the Persian Gulf, through which approximately a fifth of the world’s oil exports pass, as well as its role as host to the U.S. Fifth Fleet (which helps protect that oil), makes its continued alliance with the U.S. crucial to American energy security. As for Jordan, its long border with Iraq, which will likely host American troops for many more years, and its peace treaty with Israel, makes the country an important strategic partner for America.

The good news is that the Bahraini and Jordanian regimes are less susceptible to overthrow than those in Tunisia, Egypt and even Libya. The reason has everything to do with identity; whereas the soldiers of the those countries hailed from the same ethno-religious group as the protesters, the Bahraini and Jordanian militaries are manned by ruling minorities less sympathetic to the plight of a disenfranchised majority.

This difference goes to the core of why revolutionary groups succeed or fail. If a revolutionary group lacks a guerrilla army capable of overpowering the government’s military, their efforts can only succeed if there are mass defections from the armed forces. Because none of the revolutionary movements that have recently surfaced in the Middle East possess a guerrilla army, the extent of their success has corresponded to the scale of the military defections to their cause. In instances where the entire military leadership defected, as was the case in Tunisia and Egypt, the ruler had to resign almost immediately. On the other hand, in Libya, where only part of the military defected, a civil war erupted and the fate of the Gaddafi regime is still unclear as of this writing.

The Tunisian, Egyptian, and Libyan soldiers who refused to suppress anti-regime demonstrations did so in part because they identified with the protesters and had qualms about shooting their fellow countrymen. In each case, the soldiers and demonstrators came from the same ethno-religious group. By contrast, Bahrain’s Sunni minority, which comprises about 30 percent of the nation’s population (including the monarch and most military personnel), lords over a large Shi’ite majority. Similarly, Jordan’s monarchy and military are dominated by members of Jordan’s East Bank tribes, which represent only a third of the country’s population; largely disenfranchised Palestinians make up the rest.

Not only do Bahrain and Jordan’s soldiers not come from the same families as the demonstrators, their families actually stand to lose their privileged status if the demonstrators achieve their aims. And, since a Shi’ite-dominated Bahraini government is unlikely to trust a predominantly Sunni military to defend it, that government can be expected to alter the religious balance of the military so that it more accurately reflects the country’s religious make-up — providing a powerful disincentive for the country’s current crop of military leaders to contemplate abandoning their posts. Majority rule in Jordan would similarly end the East Bank tribes’ control over their country’s economy and military, a development the armed forces are not eager to contemplate.

History teaches that few minority-run regimes accept democratization peacefully, and the Middle Eastern record is especially blood-soaked. Following the 1991 Gulf War, revolutionaries from Iraq’s Shi’ite majority sought to oust Saddam Hussein’s Sunni-backed dictatorship. At the revolt’s height, Saddam controlled only four of Iraq’s 18 provinces and most pundits assumed that his Ba’athist regime would soon collapse. But recognizing the threat the Shi’ite rebellion posed to Sunni interests, the largely Sunni Republican Guard mercilessly quashed the insurgency with helicopter gunships and tanks, killing tens of thousands of Shi’ite civilians in the process. Similarly, when Yasser Arafat’s PLO attempted to depose Jordan’s King Hussein in 1970-71, the Jordanian military killed thousands of Palestinians and expelled the PLO from the country.

The lesson remains true today. As long as Bahrain’s Sunnis and Jordan’s East Bankers continue to oppose majority rule, few soldiers are likely to defect to the opposition. As a result, a future struggle for majority rule in Manama and Amman might end up looking a lot more like Iraq in 1991 or Jordan in 1970-71 than Tunisia, Egypt or Libya circa 2011.