Editor's note; The video above is from May 30, 2019, showing Shanahan commenting on reports about a request to hide the USS John McCain from President Trump during his visit to Japan.

Acting Defense Secretary Patrick Shanahan is resigning and pulling his name from consideration for the permanent job, President Donald Trump announced on Twitter Tuesday. Trump will have his third defense secretary in less than six months and it comes as the U.S. faces increasing tensions with Iran.

"Acting Secretary of Defense Patrick Shanahan, who has done a wonderful job, has decided not to go forward with his confirmation process so that he can devote more time to his family," Trump Tweeted.

Trump said Secretary of the Army Mark Esper will be the new Acting Secretary of Defense.

Trump announced in May that he would nominate Shanahan but the formal nomination process in the Senate had been inexplicably delayed.

USA TODAY reported Tuesday that the FBI has been looking into a domestic violence incident between Shanahan and his former wife from nine years ago. Each of them reportedly told police they had been punched by the other. Shanahan reportedly said he "never laid a hand on" her.

"Our story is not dissimilar to those of the many families facing the difficult challenges that come when a loved one struggles with substance abuse and other emotional issues as is the case with my former-wife," Shanahan reportedly wrote in a statement Monday night.

Shanahan addressed the issue again Tuesday in announcing his resignation, indicating it likely would have been brought up during his confirmation.

"After having been confirmed for Deputy Secretary less than two years ago, it is unfortunate that a painful and deeply personal family situation from long ago is being dredged up and painted in an incomplete and therefore misleading way in the course of this process. I believe my continuing in the confirmation process would force my three children to relive a traumatic chapter in our family's life and reopen wounds we have worked years to heal. Ultimately, their safety and well-being is my highest priority," Shanahan wrote.

Shanahan, a former Boeing executive, has been leading the Pentagon as acting secretary since Jan. 1, a highly unusual arrangement for arguably the most sensitive Cabinet position.

In his tenure at the department he's had to deal with a wide array of international hotspots, ranging from missile launches by North Korea to the sudden shift of military ships and aircraft to the Middle East to deal with potential threats from Iran.

Shanahan, 56, had extensive of experience in the defense industry but little in government. In more than four months as the acting secretary, he focused on implementing the national defense strategy that was developed during Mattis' tenure and emphasizes a shift from the resources and tactics required to fight small wars against extremist groups to what Shanahan calls "great power" competition with China and Russia.

Esper will be the third defense secretary -- confirmed or acting -- in the first 2 1/2 years of the Trump Administration. James Mattis held the position until Dec. 31, 2018. Mattis initially announced he would leave 

Congress Defense Budget
Secretary of the Army Mark Esper speaks during a House Armed Services Committee budget hearing for the Departments of the Army and Air Force on Capitol Hill in Washington, Tuesday, April 2, 2019. (AP Photo/Andrew Harnik)
AP