The soldiers seemed to have made little effort to hide their presence or vary their routine to make it harder for enemies to track them.

In a newsletter ISIS released shortly after the attack, the group quoted a member of its “emni,” or intelligence and security branch, based inside Manbij, who explained that the militant group had regularly tried to hit American forces in rural Manbij. Their efforts failed until last week.

In the article, the ISIS operative explained the surveillance the group had used, saying American forces were positioned at three small bases on the outskirts of Manbij. He said United States troops moved regularly among these bases in convoys of five to 10 armored cars, escorted by guard vehicles belonging to an American-backed Kurdish militia.

While it is impossible to verify the claims made in the ISIS newsletter — and the Pentagon has released no further details on the attack — the surveillance described in the article is consistent with what is known about how the group is carrying out its insurgency.

He explained that American soldiers entered the city in convoys of Land Cruisers, but rarely appeared outside their armored cars, according to a translation provided by the SITE Intelligence Group, which monitors extremist content.

“To conduct an attack like this means that ISIS was conducting intelligence and reconnaissance on the movement of U.S. soldiers and had someone pre-positioned in the city so that once they got info on timing and location they could get someone on the site pretty fast,” said Mr. Jones of the strategic and international studies group. “That means that in Manbij, they have a cell structure.”

Mr. Jones said strikes like the one on the American troops require militants to carry out intelligence, build the bomb, transport the bomb and deploy a suicide bomber.

“It shows they have a clandestine network,” he said.