Mr. Shikder is an observant Muslim who does not drink or smoke, prays regularly and wears a long black beard with a trim mustache. His own faith compounded his horror at the jihadists’ actions, he said.
“I do everything that Islam tells you to do, but my Islam did not tell me to do what they did,” he said.
He said he struggled to determine how much his wife had embraced their message.
“Sometimes I was feeling that she was stuck,” he said. “Sometimes I was feeling that she was believing what she was doing.”
Yusuf is now 8, Zahra is 4, and his wife’s other daughter, Safyah, is about 18 months old. His lawyers believe that she can claim American citizenship through her mother, and Mr. Shikder has offered to adopt her.
But it remains unclear whether the children will make it out of Syria.
Mr. Smith and Mr. Shikder have contacted American diplomats, law enforcement agents and members of the American-backed Syrian Democratic Forces that have surrounded Baghuz, hoping to secure safe passage for the children, Mr. Smith said.
Heather Fabrikant, a spokeswoman for the United States Consulate in Erbil, Iraq, said the State Department was “aware of reports of an international parental child abduction case in which U.S. citizen children were taken to Syria in 2015” but that she could not discuss details because of privacy considerations.
On Monday, Mustafa Bali, a spokesman for the Syrian Democratic Forces, wrote on Twitter that they had slowed down the offensive on Baghuz “due to a small number of civilians held as human shields” by the Islamic State. “However, we assert that the battle to retake the last ISIS holdout is going to be over soon.”
As he waits, Mr. Shikder prays, and tries to stay hopeful that his children will be saved.
“Everything is making me worried,” he said.