The U.S. Navy is working to tackle radicalism after two racist incidents aboard naval ships were reported, contributing to the Secretary of Defense’s call for the military to stand-down and address extremism in the ranks.

Senior U.S. Navy commanders met with sailors this week after a noose was found aboard a San Diego ship late last month, followed by a separate incident reported over the weekend involving hate speech that was written on the wall of another ship.

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Both incidents remain under investigation but prompted Adm. John Aquilino, Commander of the U.S. Second Fleet, to abruptly leave his post in Hawaii and fly to San Diego to address sailors aboard the USS Carl Vinson Tuesday.

"Extremism in our Navy is unacceptable. We will not tolerate it. OK? It's that simple," he said.

"I have policies in the Pacific Fleet that we do not care what race you are, what creed you are, what god you pray to, what sexual orientation you are, or what gender you are," he added.

Secretary of Defense Lloyd Austin granted each branch of the military a 60-day window to stand down and hold discussions regarding extremism amongst service members – though military officials have admitted that addressing extremism is made all the harder by the fact that it was yet to be firmly defined.

Pentagon Press Secretary John Kirby told reporters earlier this month that the Department of Defense prohibits military personnel from being involved in "supremacist, extremist or criminal gang doctrine, ideology or causes."

But many right-wing groups, like the Boogaloos and Proud Boys -- relatively new groups known for violent and extremist behavior -- have yet to be established as "gangs" or otherwise characterized. Social media has also prompted questions regarding first amendment rights, which the military has been unable to define with "uniform understanding."

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Reports have emerged following the Jan. 6 attack on the U.S. Capitol building by pro-Trump supporters that both active military and veterans were present during the riot – though the Defense Department has not confirmed how many active service members are believed to have attended.

"No matter what it is, it is…not an insignificant problem and has to be addressed," Kirby told reporters last week.

But apart from eliminating intolerance in the armed services, military officials say discrimination poses a security threat to service members and the country.

"If we don’t eliminate extremist behaviors from our Navy, then racism, injustice, indignity, and disrespect will grow and continue to keep us from reaching our potential - an inclusive, respectful, professional fighting force that answers the Nations call," Chief of Naval Operation, Adm. Mike Gilday told sailors Tuesday.

"If we must first question the intentions of our shipmate standing the watch with us, now, and especially, when taking fire, we will fail when the Nation needs us most in combat," he added.

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Though Austin, the first Black Secretary of Defense, said last week that most service members already lead by example, the changes in the military to address extremism will be a top-down effort, with commanding officials taking charge of eliminating intolerance.

"Today, and every day, our Navy must be a shining example of an organization centered on respect, inclusive of all," Gilday said in his speech Tuesday.

"Simply put, we must demand of each other that we treat everyone with dignity and respect.  That is how we will become a stronger Navy," he concluded.

Lucas Tomlinson, Jennifer Griffin and and the Associated Press contributed to this report.