EXCLUSIVE: Convicted Fort Hood shooter Nidal Hasan has written to Pope Francis espousing “jihad,” in his latest correspondence aligning himself with radical Islam.

Despite efforts by the Defense Department to label the 2009 massacre as “workplace violence,” Hasan has described himself several times, and again in the new letter, using the acronym "SoA," or "Soldier of Allah."

Hasan directed his attorney John Galligan to mail the undated, six-page, hand-written letter to the pope. A copy of the letter – titled, "A Warning To Pope Francis, Members Of The Vatican, And Other Religious Leaders Around the World” – was provided by the attorney to Fox News.

Hasan appears to make multiple references to the Koran in the letter, and includes a bulleted list of guidelines for “believers.”

In one subsection titled "Jihad," Hasan praises "The willingness to fight for All-Mighty Allah," describing it as a test that elevates the "mujahadeen" who "are encouraged to inspire the believers." He states that “fighters … have a greater rank in the eyes of Allah than believers who don’t fight."

There is no reference in the letter to the Fort Hood massacre for which Hasan was convicted on 13 counts of premeditated murder, and 31 counts of attempted murder, but no terrorism charges. Hasan currently is on death row at Fort Leavenworth in Kansas.

In late August -- as part of ongoing reporting on homegrown terrorism, "Fox Files: The Enemy Within," which included a special investigation into Fort Hood -- Fox News obtained a separate Hasan letter where he pledged his allegiance to the Islamic State (ISIS) and its leader Abu Bakr al-Baghdadi.

Asked to comment on the latest letter, Hasan's attorney said it "underscores how much of his life, actions and mental thought process are driven by religious zeal. And it also reinforces my belief that the military judge committed reversible error by prohibiting Major Hasan from both testifying and arguing how his religious beliefs" motivated his actions during the shooting.

Neal Sher, an attorney representing the Fort Hood families and their relatives, also said Hasan is “thoroughly dedicated to jihad.” The lawsuit against the Defense Department and Justice Department now involves 150 individuals.

"His jihadist leanings and willingness to commit jihad were known for years before the 2009 atrocity,” Sher said. “And ever since then, he has made it abundantly clear he believes in jihad and has attempted to justify the slaughter that took place at Fort Hood."

During the trial, Sher said Hasan attempted to testify and offer a "defense-of-others plea, in other words, he killed Americans at Fort Hood in defense of his brothers, al Qaeda and now ISIS. Yet again, it demonstrates he wasn't shying away from [the shooting], he was proud of it."

Sher likened the approach to "putting [the administration's] head in the sand. They do not want to acknowledge a terrorist attack took place on their watch on American soil. And layered over that is a good dose of political correctness."

Fox News has a standing request to interview Hasan.

Catherine Herridge is an award-winning Chief Intelligence correspondent for FOX News Channel (FNC) based in Washington, D.C. She covers intelligence, the Justice Department and the Department of Homeland Security. Herridge joined FNC in 1996 as a London-based correspondent.