An Islamic State commander described by the Pentagon as the group’s “minister of war” was likely killed in a U.S. air strike in Syria, U.S. officials said on Tuesday, in what would be a major victory in the United States’ efforts to strike the militant group’s leadership.

Abu Omar al-Shishani, also known as Omar the Chechen, ranked among America’s most wanted militants under a U.S. programme that offered up to $5 million for information to help remove him from the battlefield.

Born in 1986 in Georgia, which was then still part of the Soviet Union, the red-bearded Shishani had a reputation as a close military adviser to Islamic State leader Abu Bakr al-Baghdadi, who was said by followers to have relied heavily on Shishani.

The strike itself involved multiple waves of manned and unmanned aircraft, targeting Shishani near the town of al-Shadadi in Syria, a U.S. official said.