Syria has a new government—or does it?

Ahmed al-Sharaa, leader of the organization that overthrew Syria’s Assad regime, has “assumed the presidency of the country in the transitional phase," according to a statement last week from the military command of the current government in Damascus.

The announcement formalizes the government that has existed since Mr. Sharaa and his group, Hayat Tahrir al-Sham, made their remarkable march from Idlib to Damascus eight weeks ago. It appears to herald the foundation of a centralized Islamist government in Syria after 14 years of civil war.

But not so fast. The new rulers’ declaration is belied by a complex reality on the ground. During a recent reporting trip to Syria, I saw a broken, divided country in which many armed factions are competing. Mr. Sharaa’s “presidency of the country" is more aspiration than reality.

For starters, the HTS government doesn’t have formal control over all Syrian land. Nearly a third of Syrian territory, from the Euphrates River north to the Turkish and eastward to the Iraqi border, is ruled by the U.S.-aligned, Kurdish-dominated Syrian Democratic Forces. This authority played a major role in defeating the Islamic State terrorist group in Syria in 2019. Its rulers are determined to maintain their independent political and military capacity, albeit within the framework of a united Syria.

“Those who have come to power in Damascus, everyone knows their history," Saleh Muslim, former leader of the Kurdish Democratic Union Party, the ruling party in the Kurdish region, said in an interview. “They were part of al Qaeda. They were part of Nusra. . . . It was just a few years ago. Everyone knows what they’ve done. And now they’re in Damascus. . . . No one can force us to dismantle what we’ve built."

Aldar Khalil, a senior Democratic Union Party official, put it even more plainly: “The revolution in Syria started to destroy centralized rule in Syria, and after that’s gone, its not possible to put something new ruling from the center. That’s not acceptable."

The Syrian Democratic Forces, with more than 100,000 fighters, is the most direct barrier to the consolidation of a new, centralized Islamist regime in Syria. But it isn’t the only armed group outside Damascus’s control.

In the southwestern Suwayda Province, heartland of the Druze people, the armed Rijal al Karama group—meaning Men of Dignity—is in control in alliance with other armed factions. The group won’t let HTS fighters enter the province and is demanding a decentralized system of government. Hikmat Salam al-Hijri, a senior Druze leader in the province, recently told the Iraqi Kurdish Rudaw news channel: “We will not hand over our weapons until the state, constitution and government are formed and the decentralized system is the most appropriate system for Syria."

To the west in the Daraa province, Ahmed al-Awda, a former leader of the Sunna Youth Forces rebel group, commands an independent Sunni Arab militia. He is reputed to have the support of the United Arab Emirates.

In the west, according to the Syrian Observatory for Human Rights, HTS is engaged in military operations against groups loyal to the Assad regime. Syria’s coastal west is the hub of the Alawite community, from which the Assad family came. HTS forces, many hailing from the organization’s heartland in the northern Idlib Province, are carrying out search operations across the countryside, resulting in deaths on both sides. On Jan. 24, 10 HTS men were killed by unknown gunmen at a checkpoint near the town of Jabla. On the same day, 13 Alawites were killed in the town of Fahel.

So Mr. Sharaa, declarations notwithstanding, isn’t the undisputed president of Syria. His forces prevail in Damascus and the Idlib province. Elsewhere, things are fluid.

HTS isn’t a huge organization, and it appears hobbled by a lack of manpower as it struggles to control the region. When it seized power, it likely consisted of no more than 40,000 fighters. With these modest ranks, it now seeks to control Syria.

The manpower shortage is evident on the ground. Driving from the Euphrates Dam across the desert toward the capital on Jan. 14, I traveled about 125 miles between the last Syrian Democratic Forces checkpoint and the first HTS one. I passed many empty roadblocks deserted by the former regime. Only around the city of Homs, in an area of Alawite population, could many fighters of the new regime be found, conducting one of their sweeps.

Even in the capital, one sees scant evidence of the new authority. Plenty of HTS fighters are hanging around and holding impromptu victory processions. But the Assad regime’s police force has been disbanded, and nothing substantial has taken its place. The city is in limbo.

European and other Western officials traveling to Damascus to meet what they imagine to be the new government of Syria should bear in mind that the country remains divided. The Islamist organization controlling Damascus is only one of many groups vying for control in the region. The task it faces is consolidating its power. It’ll be up to the West to decide whether to support a new, centralized, authoritarian, Islamist Syria—or consider other options.

Mr. Spyer is director of research at the Middle East Forum and director of the Middle East Center for Reporting and Analysis. He is author of “Days of the Fall: A Reporter’s Journey in the Syria and Iraq Wars."