Brett Elliott Crozier, captain of the USS Roosevelt aircraft carrier in Guam, was fired Thursday after he wrote a four-page letter urging Navy leadership to protect sailors from the ongoing coronavirus pandemic. Crozier's dismissal drew the attention of the White House on Saturday, with President Trump endorsing the Navy's decision.

"We are not at war, and therefore cannot allow a single Sailor to perish as a result of this pandemic unnecessarily," Crozier wrote in the letter.

The message was seen by multiple sailors aboard the USS Roosevelt, and allegedly caused “panic” on the vessel. As of Saturday, 155 sailors on the USS Roosevelt tested positive for COVID-19, according to the Wall Street Journal.

Acting Navy Secretary Thomas Modly said Crozier had “exercised extremely poor judgement” by distributing the letter. Modly then relieved Crozier of his position.

Trump called Crozier’s letter “not appropriate.”

“I thought it was terrible, what he did, to write a letter. I mean, this isn't a class on literature. This is a captain of a massive ship that's nuclear powered. And he shouldn't be talking that way in a letter,” Trump said.

Democratic presidential candidate Joe Biden, on the other hand, defended Crozier.

“I think it’s close to criminal the way they’re dealing with this guy,” Biden told ABC News. “I think he should have a commendation rather than be fired.”

The Journal noted that on "Capitol Hill and inside the Pentagon, lawmakers and officials reacted with confusion and anger over the dismissal." Videos were posted of sailors cheering him and chanting, "Captain Crozier!"

Crozier, 50, had a distinguished career in the Navy. A native of Santa Rosa, California, Crozier entered the U.S. Naval Academy after graduating from high school in 1988. In 1994, he began his first assignment as a naval aviator in Barbers Point, Hawaii.

He was later deployed with the USS Nimitz supercarrier in 2003, during Operation Iraq Freedom. In 2007, Crozier attended the Naval War College, obtaining a Master’s degree in National Security and Strategic Studies.

In addition, Crozier completed the Naval Nuclear Power training program in 2014, and became the executive officer of the USS Reagan through July 2016. In June 2017, he commanded the USS Blue Ridge in Yokosuka, Japan.

The U.S. has the most cases of coronavirus in the world, and the disease could threaten the readiness of the U.S. armed forces. The large size and scope of the military makes it difficult to implement a social distancing policy that could apply to all servicemembers.

“I can’t put out a blanket policy, if you will, that we would then apply to everybody, because every situation is different,” Defense Secretary Mark Esper told reporters in March. “Tell me, how do I do six-feet distancing in an attack submarine? Or how do I do that in a bomber with two pilots sitting side by side?”

As of Sunday at 11:35 a.m. ET, there are at least 312,418 cases of coronavirus in the United States, with the domestic death toll exceeding 8,500.