Mohammed al-Bashir is an electrical engineering graduate who had been administering a sliver of rebel-held territory in northwestern Syria before he was tasked this week with heading Syria’s interim government, as the country faces many grave challenges.

Mr. al-Bashir’s appointment as caretaker prime minister was confirmed on Tuesday, days after the Islamist rebel alliance known as Hayat Tahrir al-Sham toppled the Assad regime. Mr. al-Bashir, who previously administered the Hayat Tahrir al-Sham-led government in Idlib Province, is expected to lead until March 1, 2025.

Some of the key difficulties will be to “maintain security, maintain the stability of institutions, and ensure that the state does not disintegrate,” Mr. al-Bashir said in a statement reported by Syria’s state news agency SANA on Wednesday, adding that the interim administration had “extensive experience” of governing in Idlib.

Syria has been deeply divided by 13 years of civil war, and Hayat Tahrir al-Sham has vowed to maintain security and continuity, aiming to avoid the kind of power vacuum that has followed other Arab revolutions or regime changes. The group has tried to gain international legitimacy while also being criticized for its authoritarian tactics and supports a conservative and at times hard-line Sunni Islamist ideology.

Mr. al-Bashir was born in 1983 in Jabal al-Zawiya, Idlib province, according to a website of the rebel-led administration in Idlib. The area became infamous after security forces were accused by human rights groups and others of a series of killings in 2011 soon after protests erupted against Mr. al-Assad’s rule.

Mr. al-Bashir gained a bachelor’s degree in electrical engineering from the University of Aleppo in 2007 and in subsequent years attained additional qualifications in English, administrative planning and project management, according to a website of the transitional government. In 2021, he also gained a degree in “Shariah and law” from Idlib University.

His political evolution, and how he came to support rebels fighting to overthrow Mr. al-Assad’s government, was not immediately clear. The website for the transitional government also said that in 2011, the year the civil war began, Mr. al-Bashir held a management job at the state-owned Syrian Gas Company, part of the petroleum ministry. On Wednesday, the company’s website still featured a photograph showing Mr. al-Assad touring a facility.

It is also not clear where Mr. al-Bashir was during the years that followed, or what role he may have played in the conflict, but by 2022, he had emerged as minister of development in the administrative arm of Hayat Tahrir al-Sham, which for years had held territory in Idlib.

He was appointed prime minister for that territory this year, according to the group’s website, months before the rebel alliance began the assault that overthrew the Assad government.