An Army lieutenant colonel's resignation letter is gaining attention on social media after he used it to protest the COVID-19 vaccine mandate and what he described as the "Marxist takeover of the military."

The resignation letter by Lt. Col. Paul Douglas Hague, tweeted out by his wife and shared with Fox News, said he was resigning from the Army after 19 years of service and forgoing his pension primarily because of the Pentagon's mandatory COVID-19 vaccination order for all U.S. military service members.

PENTAGON ORDERS COVID-19 VACCINATIONS FOR SERVICE MEMBERS

"First, and foremost, I am incapable of subjecting myself to the unlawful, unethical, immoral and tyrannical order to sit still and allow a serum to be injected into my flesh against my will and better judgment," Hague, who is stationed at Fort Bragg in North Carolina, wrote in the letter. "It is impossible for this so-called ‘vaccine’ to have been studied adequately to determine the long-term effects." 

The Centers for Disease Control and Prevention has said the vaccines are safe and effective. 

Hague listed multiple other reasons for his resignation, including what he views as "an ideologically Marxist takeover of the United States government at their upper echelons," and "a complete lack of confidence" in the Biden administration, which he blamed for the Kabul terrorist attack last month that killed 13 U.S. service members.

"I would like nothing more than to continue in the Army to reach my 20 years of active federal service and retire with my pension," he wrote. "However, I instead will join those who have served before me in pledging my Life, my Fortune, and my Sacred Honor to continue resisting the eternal and ever-mutable forms of oppression and tyranny – both from enemies outside our nation‘s borders, and those within."

Hague’s wife, Katie Phipps Hague, told Fox News her husband submitted the letter on Aug. 30 and that it has since been "sent up his chain of command" and appears to be "going smoothly" so far. She also sought to clarify some discrepancies in the letter that critics used in an effort to debunk the story. 

For instance, the letter is originally dated Aug. 23, but the Kabul attack occurred three days later. Phipps Hague said her husband began drafting the letter on Aug. 23, revised it multiple times, and forgot to change the original date before submitting it on Aug. 30.

Phipps Hague also responded to skeptics on Twitter who asked why her husband didn’t protest the multiple other vaccines he had to take in order to serve in the military.

"He didn’t resign over a vaccine," she responded. "He said he felt the vaccine was being used as a political tool to divide and segregate Americans. He then went on to list many other reasons for his resignation – none of which have anything to do with vaccines."

Hague confirmed to Fox News that his resignation process has begun and that he still stands by what he said.

When reached for comment, Army spokesman Lt. Col. Gabriel J. Ramirez told Fox News, "The U.S. Army does not comment on administrative actions."

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The Pentagon announced Aug. 23 that it is requiring all service members to get vaccinated against the coronavirus, effective immediately. The decision came just days after the Pfizer-BioNTech vaccine became the first to get full regulatory approval by the Food and Drug Administration.

Military lawyers have noted an uptick in calls from service members seeking to understand their rights in light of the mandate. On Monday, demonstrators organized by New Mexico Freedoms Alliance gathered at the Holloman Air Force Base Visitors Center to protest the mandate, the Alamogordo Daily News reported.