A Brooklyn man who prosecutors say twice pledged allegiance to the Islamic State group and encouraged deadly “lone-wolf” attacks in New York City’s subways and elsewhere was sentenced Wednesday to 20 years in prison.

Zachary Clark’s penalty was announced in Manhattan federal court by Judge Naomi Reice Buchwald.

The judge said she wanted to send the message that “provide or attempt to provide materials or support to a foreign terrorist organization and you will spend a very long time in jail.”

The bearded Clark, in an orange prison jumpsuit and black glasses, tried along with his lawyer to persuade Buchwald that he had reformed himself behind bars since his November 2019 arrest, in part by attending drug and anger-management programs.

But the judge remained unconvinced.

“I have no confidence Mr. Clark can be a productive and law abiding citizen,” Buchwald said as she ordered supervision for life once he is freed.

Clark, 42, pleaded guilty in August to attempting to provide support to the Islamic State group. The 20-year sentence was the maximum.

Prosecutors had requested it, noting that he posted maps and images of the subway system online in encrypted chat rooms, encouraged Islamic State supporters to attack it and urged “lone-wolf” attacks in the United States and elsewhere.

In a release, Assistant Attorney General John C. Demers said Clark provided specific instructions to others about bomb-making and how to carry out knife attacks. Prosecutors say Clark’s guidance included posting a manual entitled: “Make a bomb in the kitchen of your Mom.”

“Zachary Clark will no longer spend his time in chat rooms supporting terrorist ideals, but behind bars in federal prison for the next 20 years,” William F. Sweeney Jr., head of New York’s FBI office, said.

Dermot Shea, commissioner of the New York City Police Department, said Clark claimed in his online propaganda to aspire to be a martyr on U.S. soil and credited his arrest on law enforcement’s anti-terror “intelligence sharing, joint investigation, and prosecution, which results in prevention.”

In court, Assistant U.S. Attorney Matthew Hellman countered defense claims that Clark made no secret of online pronouncements by saying he never used his real identity and utilized encrypted platforms “because he was aware of law enforcement scrutiny and hoped to avoid it.”

Claims that Clark rejected radical violent ideology before his arrest were “belied by the evidence,” Hellman said. He added that law enforcement authorities were left to wonder who was radicalized as a result of materials Clark posted online.

Defense attorney Jonathan Marvinny urged the judge to reject the “parade of horribles” suggested by the prosecutor and recognize that his client was trying to turn his life around after disavowing the Islamic State group.

Given a chance to speak, Clark told the judge: “To say I’m sorry would be a great understatement.”

“I take full responsibility,” he added.