Rebels are asserting control in Damascus as Israel and other countries carry out military operations.

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As a rebel alliance tries to create a transitional government for Syria, armed factions and outside powers are still fighting to fill the void left by retreating government forces.

Kurdish-led fighters in northern Syria who are backed by the United States said early Wednesday that they had agreed to a U.S.-brokered cease-fire in Manbij, a city where they have been battling to fend off forces backed by Turkey.

And the Israeli military has launched hundreds ofairstrikes against military assets across Syria in recent days, saying it was trying to keep them out of the hands of Islamist extremists.

Here’s a guide to understanding where things stand in Syria, and what may come next.

Here’s what you need to know:

• Who’s in charge?
• Who is Ahmed al-Shara?
• What is Israel doing in Syria?
• What is Turkey doing?
• What is the U.S. doing?
• What are the internal factions in Syria?

Who’s in charge?

Hayat Tahrir al-Sham, whose name means Organization for the Liberation of the Levant, was the main rebel group leading the latest offensive, launching a surprise assault in late November from northwestern Syria that quickly led to the fall of President Bashar al-Assad. It is now leading the transition to a new Syrian government.

Mohammed al-Bashir, a rebel leader affiliated with Hayat Tahrir al-Sham, announced in a brief address on Syrian television on Tuesday that he was assuming the role of caretaker prime minister until March. 1. Mr. al-Bashir previously served as the head of the administration in rebel-held territory in the northwest.

The alliance said it would grant an amnesty for lower-level government workers and soldiers, but vowed to hunt down and punish senior officials of the previous regime who were implicated in torture and other abuses.

“We will not relent in holding accountable the criminals, murderers, and security and military officers involved in torturing the Syrian people,” said Ahmed al-Shara, the leader behind the rebel push, who was formerly known by the nom de guerre Abu Mohammad al-Jolani.

The group is a former affiliate of Al Qaeda that broke with the older group years ago and came to dominate Idlib, the last stronghold of Syria’s opposition during the 13-year civil war.

Geir Pedersen, the United Nations’ special envoy for Syria, said on Tuesday that Hayat Tahrir al-Sham and other armed groups controlling the capital had issued “reassuring statements” about forming a government of “unity and inclusiveness.” He urged Syria’s armed groups to protect civilians and create a government that represented the country’s many ethnic and religious communities.

But he warned of the dangers of renewed violence among the patchwork of groups operating across Syria and of the risks posed by what he called Israel’s “very troubling” military operations in the country.

Who is Ahmed al-Shara?

Mr. al-Shara of Hayat Tahrir al-Sham recently gave up his nom de guerre, Abu Mohammad al-Jolani, after concluding the shocking military offensive that unseated the Assad regime.

He was born Ahmed Hussein al-Shara in Saudi Arabia, the child of Syrian exiles, according to Arab media reports. In the late 1980s, his family moved back to Syria, and in 2003, he went to neighboring Iraq to join Al Qaeda and fight the U.S. occupation.

He spent several years in an American prison in Iraq, according to the Arab media reports and U.S. officials. He later emerged in Syria around the start of the civil war and formed the Nusra Front, which eventually evolved into Hayat Tahrir al-Sham.

Since breaking ties with Al Qaeda, Mr. al-Shara and his group have tried to gain international legitimacy by putting aside global jihadist ambitions and focusing on organized governance in Syria.

Questions have emerged about what kind of government Mr. al-Shara would support and whether Syrians would accept it. In Idlib, Hayat Tahrir al-Sham has espoused a government guided by a conservative and at times hard-line Sunni Islamist ideology.

Since the rebel offensive began, Mr. al-Shara has sought to reassure minority communities from other sects and religions. Some analysts say he now faces the test of his life: whether he can unite Syrians.

What is Israel doing in Syria?

Israel is carrying out intensive airstrikes on military targets that were controlled by the Assad government. Its ground forces have advanced beyond the demilitarized zone on the Israel-Syria border, their first overt entry into Syrian territory in more than 50 years.

Israel said on Tuesday that it had destroyed Syria’s navy in overnight airstrikes, as it continued to pound targets in Syria despite warnings that its operations there could ignite new conflict and jeopardize the transition of power to an interim government.

Israel’s defense minister, Israel Katz, said that the Israeli military had “destroyed Syria’s navy overnight, and with great success.” Photos from the Syrian port city of Latakia showed the smoldering remains of ships sunk at their dock.

Mr. Katz said that Israel’s military “has been operating in Syria in recent days to hit and destroy strategic capabilities that pose a threat to Israel.” He did not explain what new or immediate risk Syria’s navy presented to Israel, which has the most powerful military in the Middle East.

On Tuesday, an Israeli military spokesman denied reports that the military was advancing on Damascus. The spokesman, Avichay Adraee, said the military was inside a buffer zone between Israel and Syria and at other points “in order to protect the Israeli border.”

Prime Minister Benjamin Netanyahu said Israel “would like to form relations with the new regime in Syria,” but said he had approved the bombing of Syrian military targets “so that those don’t fall into jihadists’ hands.”

What is Turkey doing?

Fierce fighting was underway on Tuesday between rebels supported by Turkey and U.S.-backed, Kurdish-led forces near Kobani, a town in northern Syria with historical and symbolic significance.

On Tuesday, Turkish-backed fighters were “violently attacking” in the vicinity of Kobani, said Farhad Shami, a spokesman for the U.S.-allied forces. Both he and an independent group monitoring the war said Turkish warplanes were assisting their allies on the ground with airstrikes.

Turkey and the United States, allies in NATO, both welcomed the fall of the Assad government over the weekend. But one of Turkey’s central strategic goals in the region is to weaken Kurdish forces, putting it at odds with Washington.

Turkish-backed forces captured the city of Manbij on Monday, according to the Syrian Observatory for Human Rights, a monitoring group based in Britain, and pushed north toward Kobani, less than 40 miles away.

On Tuesday, the Kurdish forces there announced a cease-fire brokered by the United States.

What is the U.S. doing?

The main U.S. interest in Syria is the defeat of the Islamic State, also known as ISIS, which maintains a presence in the northeastern and central parts of the country. About 1,000 U.S. Special Operations troops are housed in bases in the east and northeast of the country, often working closely with Syrian Kurdish troops.

President Biden authorized U.S. airstrikes on Sunday against Islamic State camps and operatives inside Syria. A swarm of B-52, F-15 and A-10 warplanes hit more than 75 targets in central Syria, according to U.S. officials.

He said the United States would support the region “should any threat arrive from Syria during this period of transition.”

“We’re cleareyed about the fact that ISIS will try to take advantage of any vacuum to re-establish its capability, to create a safe haven,” Mr. Biden said. “We will not let that happen.”

What are the internal factions in Syria?

In addition to Hayat Tahrir al-Sham, there are several major armed groups in Syria, and many smaller ones.

Syrian Democratic Forces

Forces from Syria’s Kurdish ethnic minority, which makes up about 10 percent of the population, became the United States’ main local partner in the fight against the Islamic State in Syria, under the banner of the Syrian Democratic Forces.

After the Islamic State was largely defeated in 2019, the Kurdish-led forces consolidated control over towns in the northeast, expanding an autonomous region they had built there. But Kurdish fighters still had to contend with a longtime enemy, Turkey, which regards them as linked to Kurdish separatist insurgents in Turkey.

Syrian National Army

This umbrella group, which includes dozens of groups with different beliefs, receives funding and arms from Turkey, which has long been focused on expanding a buffer zone along its border with Syria to guard against the activities of Kurdish militants.

Turkey wants to create an area where it can resettle some of the three million refugees who have fled Syria and are living within its borders. But it has struggled to harmonize the ragtag groups that make up the Syrian National Army.

The group is largely composed of the dregs of the Syrian civil war, including many fighters whom the United States had rejected as criminals and thugs. Some received training from the United States early in the war, but most were dismissed as too extreme or too criminal. Most have no clear ideology and had turned to Turkey for a paycheck of about $100 a month when the group was formed.

The Druse militia

Syria’s Druse minority is concentrated in Sweida, an area in the southwest. This week, Druse fighters joined the push to topple the Assad regime, launching an offensive in the southwest and clashing with government forces, according to media reports.

The Druse fighters are part of a newly formed group of Syrian rebels, which includes fighters from other backgrounds, working under the name the “Southern Operations Room.”

The Druse are a religious group practicing an offshoot of Islam, developed in the 11th century, that contains elements of Christianity, Hinduism, Gnosticism and other philosophies. There are more than one million Druse across the Middle East, mostly in Syria and Lebanon, with some also in Jordan and Israel.

Islamic State

The Islamic State in Iraq and Syria, better known as ISIS, seized vast stretches of territory in Syria and Iraq in 2014, establishing a brutal caliphate before it was beaten back by a U.S.-led coalition. Now its members are largely in hiding.

Lately, there have been signs of the group’s resurgence in Syria amid wider instability in the region. The Pentagon warned in July that Islamic State attacks in Syria and Iraq were on track to double compared with the previous year. The group has repeatedly tried to free its members from prisons and has maintained a shadow governance in parts of northeastern Syria, the U.S. said.

On Tuesday, Islamic State forces killed 54 people in the Homs region in central Syria who had been part of the Syrian government’s military and fled during the collapse of the Assad regime, according to the Syrian Observatory for Human Rights.

Reporting by Neil MacFarquhar, Farnaz Fassihi, Vivian Yee, Samuel Granados Matthew Mpoke Bigg, Raja Abdulrahim, Adam Rasgon, Ephrat Livni and Thomas Fuller