The tangled alliances and rivalries in Syria

Relationships in the Middle East are complicated. Now, the sudden ouster of President Bashar Assad of Syria is shaking up the region again. Years-old alliances have crumbled, and global powers are weighing how to deal with Syria's new de facto leaders, a little-known group of rebels that many countries had rejected as extremists. Here's a primer:

When Assad was in control

Only weeks ago, Assad still ruled most of Syria. He was backed by close allies: Iran, Russia and Hezbollah, a Lebanese militia supported by Iran.

In 2011, his forces brutally cracked down on peaceful anti-government protesters, setting off an armed rebellion. Over nearly 14 years, the civil war spiraled into a multisided conflict involving rebels, extremists and others. Hundreds of thousands of people were killed during the war.

Other armed factions that weren't primarily there to oppose the government also grew amid the power vacuum. The Islamic State group spread from Iraq into Syria, and Syria's Kurdish ethnic minority created an autonomous region.

Some of the armed groups that gained territory during the civil war also fought one another. In northern Syria, militias backed by Turkey, Syria's neighbor, spent years battling Kurdish forces. Turkey has tried to stamp out Kurdish separatists at home for decades, and the Turkish government sees Kurdish fighters so close to their border as a threat.

But the Kurds were also a key partner for the United States. To fight the Islamic State group in Syria, Washington armed, trained and funded forces that were led and dominated by Kurdish fighters. That set up lingering tension between the United States and Turkey, which are both NATO members.

At its peak, the Islamic State group controlled about a third of Syria. Several groups ultimately weakened the terrorist group: primarily the Kurdish-led forces, which were supported by U.S. airstrikes, but also Syrian government forces backed by government allies and rebels sponsored by Turkey.

With rebels in control

But long-standing relationships in Syria were turned upside down in December when a coalition of rebels from the north swept to Damascus, the capital, eventually joined by rebels who banded together in the south. In less than two weeks, they toppled Assad, whose family had governed for a half-century.

Assad fled to Russia after his allies, burdened by their own wars, largely abandoned him. Moscow has been bogged down with its invasion of Ukraine. Iran has been drained by more than a year of conflict with Israel. And Hezbollah is battered after fighting Israel in Lebanon.

The rebels who took charge in Damascus were led by Hayat Tahrir al-Sham, which has for years governed part of northwestern Syria, next to the Turkish border. Turkey, whose tacit support for the group has helped it flourish, became one of the first global powers to meet with Syria's new de facto leaders.

Along with Turkey, Qatar was already in contact with the rebels well before the surprise offensive. Both have reopened their embassies in Damascus.

Although they propped up Assad against the rebels for more than a decade, Iran and Russia aren't openly antagonizing Syria's new leadership. Russia is talking to those in charge about keeping its military bases in Syria. Iran might still work to undermine stability in Syria, which it sees as strategically vital. But for now, it has asked for -- and received -- assurances that Syria's Shiite Muslims will be protected, according to its foreign minister.

Hayat Tahrir al-Sham used to be affiliated with al-Qaida. The United States, the European Union and the United Nations have designated Hayat Tahrir al-Sham as a terrorist entity for years. But the group publicly broke with al-Qaida years ago, and presents itself as moderate.

Many countries are now rethinking the group's terrorist designation so that they can establish formal relationships with those leading the new Syria. If that happens, the next step could be lifting heavy sanctions Western countries had put on Assad so that Syria can rebuild and repair its economy.

The United States sent senior diplomats to meet with the rebels in mid-December. Diplomats from Britain, the EU, France, Germany, Italy, Switzerland and the United Nations had already met with them. And Britain has said it is considering dropping the terrorist designation.

Since Assad fled, Israel, which captured parts of southern Syria in 1967, occupied more territory and struck hundreds of Syrian military sites, destroying Syria's navy and dozens of weapons stores and striking some air bases. The head of the rebel coalition that now governs Syria spoke out against what he called Israel's "unwarranted" escalation, but said Syria could not handle any more conflict.

The upheaval leaves Arab states such as Egypt, Jordan, Saudi Arabia and the United Arab Emirates in a tricky spot. While they had little love for Assad, they were largely resigned to working with him. And in other parts of the region, they have fiercely opposed Islamist groups like the one now running Syria. Several Arab representatives met with the rebels recently. But they remain wary.

With the parade of international officials arriving in Damascus, the new authorities appear to be making rapid progress toward international recognition.

There is a lot for the transitional authorities to do inside Syria: stabilize and secure the country, restore public services, reconstitute a government, welcome what could be millions of returning refugees, rebuild the shattered infrastructure and economy and win justice for abuses committed during the war.

But the country's new leaders will also have to look outward, balancing the tangled, sometimes contradictory interests of many foreign powers -- some friendly, some hostile, some wary.

Some of those countries hold the keys to helping Syria recover from war by sending aid and lifting sanctions. If they withhold help, however, or if too many outside powers meddle or compete with one another in Syria, analysts say the country could face more conflict, fragmentation and tragedy.