U.S. Army Command Sgt. Maj. John Wayne Troxell, the senior enlisted adviser to Gen. Joseph F. Dunford, the chairman of the Joint Chiefs of Staff, speaks on the flightline of Al Dhafra Air Base in the United Arab Emirates on Dec. 22. (Tech. Sgt. Anthony Nelson Jr./Air Force)

The Pentagon’s senior enlisted service member has issued a blunt warning to Islamic State fighters, saying in new social-media posts that they could either surrender or face death in a number of forms, including being beaten to death with steel entrenching tools.

Army Command Sgt. Maj. John Wayne Troxell, the senior enlisted adviser in the Pentagon, issued the warnings on Facebook and Twitter. Senior U.S. officials, including Defense Secretary Jim Mattis, have warned Islamic State fighters for months that they must lay down their weapons or face annihilation, but Troxell’s message was unusually forceful.

“ISIS needs to understand that the Joint Force is on orders to annihilate them,” Troxell wrote on Facebook. “So, they have two options should they decide to come up against the United States, our allies and partners: surrender or die!”

Troxell added that the U.S.-led military coalition will provide militants who surrender with safety in a detainee cell, food, a cot and legal due process.

HOWEVER, if they choose not to surrender, then we will kill them with extreme prejudice, whether that be through security force assistance, by dropping bombs on them, shooting them in the face, or beating them to death with our entrenching tools,” Troxell wrote. “Regardless, they cannot win, so they need to choose how it’s going to be.”

The posts were published Tuesday night along with a photograph of an entrenching tool — a collapsible shovel used by U.S. troops.

It isn’t the first time that Troxell has issued a warning along those lines. He used the same talking points during a United Services Organization (USO) holiday tour last month in which he and his boss, Marine Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff, visited deployed U.S. troops in numerous locations.

Video recorded by a Stars and Stripes reporter on Dec. 24 in Afghanistan shows Troxell delivering a speech to cheering troops as Dunford and Florent Groberg, a Medal of Honor recipient looked on. Troxell, speaking from a stage, said that ISIS will be “annihilated, period!” before he launched into specifics.

“That may be through advising, assisting and enabling the host-nation partners,” he said. “It may be by dropping bombs on them. It may be by shooting them in the face. And it even might be beating them to death with your entrenching tool, but we are going to beat this enemy!”

The crowd of service members assembled roared in response.

Air Force Col. Patrick Ryder, a spokesman for Dunford and the Joint Staff, said that Troxell’s comments emphasized the sincerity of the U.S.-led coalition’s resolve to defeat the Islamic State over the last four years. Ryder noted the count atrocities that the militants have committed against men, women and children.

“His intent was to communicate the tenacity of the warrior ethos that, even when faced with the brutal and unforgiving nature of combat, will use every resource available to fight and win,” Ryder said of Troxell.

The posts include the new hashtag #ISIS_SurrenderOrDie.

As Dunford’s senior enlisted adviser, Troxell is assigned to serve as a voice for enlisted service members at the Pentagon. He frequently gives U.S. troops fiery pep talks and thanks them for their work, as many sergeants major do.

As the territorial caliphate of the Islamic State nears its end, the Post's Liz Sly reflects on its rise and ongoing fall and discusses what could come next in the Middle East. (William Neff/The Washington Post)

Troxell, who has deployed in combat five times, traveled to Syria twice last year. In October, he visited Raqqa, the Islamic State’s former de facto capital that U.S.-backed forces seized. In comments published by the Pentagon afterward, he said commanders of the U.S.-backed forces were warning the militants to surrender.

“There is no negotiating with these guys,” Troxell said. “They are either going to surrender or they are going to get killed.”

This post was originally published at 4:53 p.m. on Jan. 10 and updated with additional comments from Col. Patrick Ryder on Jan. 11.