The Islamic State issued on Thursday what appears to be the first recording in nearly a year of its reclusive leader, Abu Bakr al-Baghdadi, a move that seems intended to silence rumors of his death and to galvanize his pummeled troops.

The 46-minute audio recording would be the first time since last November that supporters of the jihadist group have heard the voice of their self-proclaimed caliph.

Since then, the group has lost significant territory, including Mosul, Iraq, which had been the largest city under its control, and much of the group’s capital, Raqqa, Syria.

In the recording, Mr. Baghdadi praised his foot soldiers for waging a tenacious battle in Mosul.

“They fulfilled their promise and their responsibility, and they did not give up except over their skulls and body parts,” he said. “Thus they were excused, after nearly a year of fighting and confrontation.”