For decades, politics in most of the Middle East has been frozen like a fossil in amber. Monarchies and pseudo-republics denied their people meaningful participation and representation. Aging presidents-for-life clung to power, grooming sons to replace them. Well-connected elites amassed wealth while burgeoning young populations struggled to find jobs.

The amber has shattered. Mideast dictators have fallen to people power, not U.S.-led regime change. Now the critical question is who will replace these leaders?

The end of this era could be a net-positive for the United States if more democratic governments take hold. In the short term, though, these developments bring with them potential threats to U.S. interests: safeguarding oil supplies, protecting Israel, fighting terrorism and containing the current Iranian regime. The biggest impact may be regional dynamics that curb Israel from attacking foes in Gaza, Lebanon and Iran.

With the proviso that this fateful year in the Middle East is just beginning, what follows are snapshots of six pivotal nations whose post-revolution politics and policies will impact U.S. national security:

Egypt

The most populous Arab nation, Egypt has vied with Saudi Arabia as the premier Arab ally of the United States. Once the trend-setter in Arab politics, culture and diplomacy, Egypt stagnated during Hosni Mubarak’s 30-year reign. With Mubarak’s resignation Feb. 11, a “supreme defense council” led by Defense Minister Mohamed Hussein Tantawi is leading the transition. The military has promised to submit a new constitution to a referendum and then hold elections for a new parliament and president.

Mubarak’s successor is likely to maintain the 1979 peace treaty with Israel—even if the Muslim Brotherhood, the oldest Islamic political group in the modern Middle East, gains a major share in the next government. As a nation that relies on tourism, Egypt cannot afford to renounce peace with Israel or to impose Islamic law. The Egyptian military will not want to jeopardize its supply of U.S. military hardware. However, a more democratic Egypt will not be silent if Israel attacks Gaza again as it did in 2008-2009, or Lebanon in 2006. Egypt is likely to lift a blockade on Gaza imposed after Hamas seized the enclave in 2007, making it easier for Hamas to smuggle weapons via the Sinai desert. Egypt may also restore diplomatic relations with Iran, which the U.S. will see as a blow to its containment strategy. Already, the interim government permitted an aging Iranian warship and supply vessel to transit the Suez Canal and enter the Mediterranean—the first such crossing since the Iranian revolution.

On counterterrorism, the Egyptian government is less likely to make mass arrests or to accept, via rendition, terror suspects caught elsewhere by the United States.  Bruce Riedel, a former senior National Security Council official and CIA officer dealing with the Middle East, said that a less repressive Egyptian government will benefit U.S. interests in the long term by diminishing the pool of recruits for al-Qaida. Still, the transition may be dicey. “While we may lose on the tactical level, we may gain on the strategic level,” he said.

Saudi Arabia

Saudi Arabia is the region’s great economic prize, sitting on top of one fifth of the world’s known oil reserves. King Abdullah, who has ruled officially since 2005 and de facto since 1995, is progressive in Saudi terms and has introduced a few modest reforms. Still, the upheaval nearby was sufficient for the king to rush home from Morocco, where he had been recuperating after back surgery. Reaching into his government’s deep pockets, he promised $37 billion in new government handouts to civil servants and students.

Gregory Gause, a Saudi expert at the University of Vermont, noted that major flooding in Jeddah in January which killed 10 people and caused severe property damage did not provoke mass protests. “If there was ever a time when people would take to the streets, this would have been it,” Gause said. The monarchy benefits, he said, from the fact that its opposition is divided between liberals and religious conservatives and so far remains a largely online phenomena However, last month a group of more than 100 Saudi intellectuals signed a petition for additional reforms, including an elected advisory council. Thousands of Saudis have signed onto Facebook and Twitter accounts calling for mass protests on March 11, the ninth anniversary of a fire in Mecca that killed 15 girls who were prevented from leaving a burning school without their Islamic cloaks.

Saudi security forces appear to have suppressed the main recent threat to the regime from al-Qaida, whose founder was Saudi-born. U.S. concerns focus on Saudi succession and preventing disruptions to Saudi oil production. Abdullah is 87 and in poor health; his half brother and crown prince, Sultan, is also an octogenarian and ailing. Third in line is the slightly younger Prince Nayef, the interior minister, who is not popular. The kingdom’s youth resent the stipends doled out to 7,000 Saudi princes and the foreign workers who take both high-paying and menial jobs. Saudi Arabia’s minority Shiite population, which predominates in the Eastern Province where most Saudi oil is produced, faces discrimination and has protested in the past. The Saudi leadership fears contagion from Bahrain, the scene of unprecedented political tumult in recent weeks. The two countries are connected by a 16-mile causeway.

Bahrain

Bahrain is a major concern for U.S. policymakers because of its sectarian divide and location. Not only is it linked to Saudi Arabia’s Eastern Province, but it is home to the U.S. Fifth Fleet, which guards the Persian Gulf and its precious oil traffic. The fleet also is a buffer between Iran and the region’s fragile sheikhdoms and emirates. From that base, some 3,000 U.S. military officers oversee 30 ships and 30,000 sailors.

Bahrain’s ruling al-Khalifa family badly mishandled protests that broke out Feb. 14, allowing masses of demonstrators to assemble in a roundabout called Pearl Square and then sending in troops to fire on sleeping protesters. The show of force drew worldwide condemnation and the regime has since made a series of concessions, freeing political prisoners, calling for dialogue, dismissing a few cabinet ministers, allowing a once-banned opposition leader to return from exile and permitting demonstrators to refill Pearl Square.

These gestures have not appeased the protesters. Shiite Muslims make up about 70 percent of the island state’s half million citizens and are demanding parliamentary reforms and an end to discrimination in employment, education and housing. Calls to overturn the Sunni Khalifas—or at least restore a more democratic, single-chamber parliament, which briefly existed in the 1970s—are growing. Saudi analyst Gregory Gause said King Hamad is “caught between his population and his family” which holds virtually all key government offices, including that of prime minister; Hamad’s uncle has been in that position since Bahrain’s independence from Britain 40 years ago. Given Bahrain’s sectarian divide and Iran’s proximity, Saudi Arabia and the U.S. worry about Iranian encroachment although so far Bahraini protesters have emphasized their nationalism by wrapping themselves literally in Bahraini flags.

Iran

Iranian officials from Supreme Leader Ali Khamenei to President Mahmoud Ahmadinejad and government-appointed leaders of Friday prayers have been crowing that Arab demonstrators are following a script written 32 years ago in Iran. Certainly, Tehran has enjoyed seeing the toppling of secular, U.S.-backed dictators but there is no indication that the protesters were motivated by a desire for Iranian-style theocracy. In fact, the uprisings have been marked by the absence of slogans such as “Islam is the Solution” and that old Iranian favorite, “Death to America.”  On Feb. 14 and Feb. 20, protests boomeranged back to Iran as the Green Movement that erupted following disputed June 2009 presidential elections returned to the streets of major Iranian cities. Tehran in recent days has resembled an armed camp as more demonstrations erupt.

Mehdi Khalaji, an Iran analyst at The Washington Institute for Near East Policy, said that if the Arab revolts had taken place before Iran’s post-election crisis, “Iran could have used it in the framework of its propaganda.” Now, Khalaji said, such claims look hypocritical, even laughable. In the short term, Iran may benefit from the distraction of Western policymakers. Since Jan.1, the regime has executed 120 prisoners, according to the International Campaign for Human Rights in Iran, giving Iran the dubious distinction of executing more people per capita than any other nation. While global media attention was focused on Libya, Iranian authorities on Feb. 24 arrested two opposition leaders and their wives.

Disruption of oil production in Libya and general uncertainty in the region have boosted oil prices and Iran’s revenues. Prospects for an attack on Iran’s nuclear program by either Israel or the United States have decreased as those countries focus on the instability among once-trusted Arab allies.

However, in the longer term, the Iranian regime faces major challenges. New heroes are emerging in the Arab world, supplanting Ahmadinejad, Khamenei and Lebanese protégé Hassan Nasrallah, the leader of Hezbollah. A more democratic Egypt may earn it a bigger diplomatic role, diminishing Iranian influence in Iraq, Lebanon and the Persian Gulf. In the interim, Turkey—a prosperous democratic state with diplomatic ties to all its neighbors—is a far more attractive regional model than Iran. The Iranian government must also content with a young, Internet-savvy generation, international economic sanctions, and cyber-warfare attacks on its nuclear program.

Israel

Israel can take comfort in the fact that for once, protests in the Arab world have had nothing to do with Israel, the Palestinians or Lebanon. Nevertheless, Israelis worry that successor governments in Egypt and elsewhere may be less accommodating to their actions against Arabs. A future Egyptian president will not “sit on the sidelines” if Israel decides to attack Gaza or Lebanon again, Riedel said. “The Egyptians are not going to be as passive.  This is going to be the major source of friction between Cairo and Washington.”

There is also the question of what impact the unrest will have on Palestinian governments in both the West Bank and Gaza. Palestinian President Mahmoud Abbas has promised new elections and efforts to reunify with Hamas, which seized control of Gaza in 2007. Successors to Abbas and to Palestinian Prime Minister Salam Fayyad may be less willing and capable of reaching a bargain with Israel.

The Obama administration said it remains determined to push for an Israeli-Palestinian settlement. Dennis Ross, the top White House official in charge of Middle East policy, recently said that the lesson Israel should draw from the fall of Mubarak is “the danger of getting stuck in an unsustainable status quo.” The Palestinians’ higher birth rate, the need to give new Arab leaders a stake in peace, and the increasingly sophisticated arsenals of Hamas and Hezbollah all argue for reaching a settlement with the Palestinians sooner rather than later, Ross said. However, Israeli Prime Minister Benjamin Netanyahu, already risk averse when it comes to making concessions for peace, is likely to become even more so as he waits to see what kind of government emerges in Egypt and whether any other pro-Western Arab dominos—such as Jordan—will fall. U.S. domestic politics may make it less likely that President Obama will pressure Netanyahu to give up more land for peace. One possibility is that Netanyahu might instead explore a settlement with Syria that could undercut Iranian influence and the possibility of a new Israeli confrontation with Hezbollah.

Libya

Libya is important to the United States because it is a major oil supplier to Europe, and like Egypt and Saudi Arabia, has both spawned and confronted numerous members of al-Qaida. A major U.S. concern is that Islamic fundamentalists will fill the vacuum left by Moammar Gadhafi’s brutal regime.

During his 41-year rule, Gadhafi prevented the creation of political parties. He staged phony “people’s congresses” while dictating policy behind the scenes and parceling out plum positions and business opportunities to members of his family and tribe. Whenever he sensed a threat, he reshuffled officials, leading one Libyan a decade ago to compare his countrymen to “mice in a bag” that Gadhafi would shake periodically to pre-empt opposition from organizing. Despite their lack of experience in politics or civil society institutions, Libyans in the eastern part of the country first liberated from Gadhafi’s rule are already putting together provisional governments. A pool of talented Libyans including returning exiles should be able to form a credible new administration. However, the transition is Libya has already been bloodier than in neighboring countries and there is a prospect of civil warfare between tribes and regions. Al-Qaida would likely take advantage of such chaos. Still, it is hard to imagine that Gadhafi’s successors will be worse stewards of Libyan interests or more menacing to the world at large than he has been.

Barbara Slavin has reported on the Middle East for more than three decades, and is the author of the 2007 book Bitter Friends, Bosom Enemies: Iran, the US and the Twisted Path to Confrontation.