WASHINGTON — Syria’s 13-year civil conflict has returned to prominence with an unexpected rebel onslaught on Aleppo, one of the country’s largest cities and an ancient business hub. The rebels are making their greatest drive in years in a war whose destabilizing ramifications have spread far beyond the country’s borders. It was the first rebel strike on Aleppo since 2016, when a savage air campaign by Russian airplanes assisted Syrian President Bashar Assad in retaking the northern city. Russia, Iran, Iranian-allied Hezbollah, and other forces have intervened, allowing Assad to retain power in Syria, which accounts for 70% of the country.

It was the first rebel strike on Aleppo since 2016, when a savage air campaign by Russian airplanes assisted Syrian President Bashar Assad in retaking the northern city. Russia, Iran, Iranian-allied Hezbollah, and other forces have intervened, allowing Assad to retain power in Syria, which accounts for 70% of the country. The increase in fighting has raised the risk of another deadly front reopening in the Middle East, at a time when US-backed Israel is fighting Hamas in Gaza and Hezbollah in Lebanon, both of which are Iranian-allied.

Robert Ford, the United States’ former ambassador to Syria, cited months of Israeli raids on Syrian and Hezbollah targets in the area, as well as Israel’s cease-fire with Hezbollah in Lebanon last week, as factors allowing Syria’s rebels to advance. Here are some of the most important characteristics of the new fighting style:

For 13 years, Assad has been at war with opposition forces seeking his downfall, resulting in an estimated half-million deaths. Some 6.8 million Syrians have fled the nation, contributing to a shift in Europe’s political landscape by fueling anti-immigrant extreme right movements. Approximately 30% of the country is controlled by opposition forces and foreign troops. The United States has approximately 900 troops in northeast Syria, distant from Aleppo, to defend against the Islamic State’s rebirth. Both the United States and Israel carry out occasional strikes in Syria against government forces and Iran-allied militias. Turkey has forces in Syria as well, and it has sway over the vast coalition of opposition forces invading Aleppo.