The man appointed as special counsel to investigate whether President Trump's campaign collaborated with the Russians is a Marine veteran who served in Vietnam.

Former FBI director Robert Mueller enlisted in the Marine Corps after the death of his college friend David Hackett, who was killed in Vietnam in 1967. Muller reportedly shipped out to Vietnam after completing Officer Candidates School.

"One would have thought that the life of a Marine, and David's death in Vietnam, would argue strongly against following in his footsteps," Mueller said in a speech for the College of William and Mary's May 2013 commencement ceremony. 

"But many of us saw in him the person we wanted to be, even before his death. He was a leader and a role model on the fields of Princeton. He was a leader and a role model on the fields of battle as well. And a number of his friends and teammates joined the Marine Corps because of him, as did I."

Mueller, a 1966 Princeton graduate, served as a Marine officer for three years, leading a rifle platoon with the 3rd Marine Division in Vietnam, according to his official FBI biography. His military awards include the Bronze Star, Purple Heart, Navy Commendation Medals and the Vietnamese Cross of Gallantry.

"I do consider myself fortunate to have survived my tour in Vietnam," Mueller said in the commencement speech. "There were many – men such as David Hackett – who did not. And perhaps because of that, I have always felt compelled to try to give back in some way. I have been lucky to spend the better part of my professional life in public service, and to benefit from the intangible rewards that come from such service."

As special counsel, Mueller has the authority to prosecute any crimes uncovered by the investigation into the Trump campaign. President Trump issued a statement on Wednesday reiterating his stance that "there was no collusion between my campaign and any foreign entity."