After Trump announced his selection on Thursday, Democrats joined many Republicans, who control majorities in both houses of Congress, to heap praise on Mattis.
"I mean (Trump) told everyone that he thought that we needed to return to torture".
The question is, how big of a problem is this for Mattis' confirmation chances?
On what's been dubbed his "thank you" tour, Mr. Trump joking asked the crowd not to tell anyone he's appointed retired Marine Corps Gen. James "Mad Dog" Mattis as defense secretary. The president-elect is also said to be considering David Petraeus, another retired Army general, as secretary of state, and retired Marine General John Kelly to head the Department of Homeland Security.
Those experiences can have markedly varied effects, making some officers a bit cautious when considering plans to send troops into battle but making others more likely to urge aggressive military responses to national security crises and less patient with the slow pace of diplomacy.
"That a person who has within ten years been on active duty as a commissioned officer in a Regular component of the armed services shall not be eligible for appointment as Secretary of Defense". If confirmed, he might also be a calming influence on Mike Flynn, the irascible former general Trump has chosen to be national security adviser - someone Mattis outranked in the military by a star.
Litjens said she understands the concern over civilian control but argued Mattis deserves to be another exception to the rule.
Chris Murphy, another Senate Democrat, said on Friday he was "deeply fearful" that the precedent of civilian control of the military could wither, although he would talk to Mattis and spoke highly of the military leader.
As a tribute to Mattis' leadership, then Secretary of Defense Chuck Hagel attended the change of command ceremony when Mattis left MacDill Air Force Base. The President-elect will need additional Congressional support to back a special waiver enabling his nomination.
"America will be fortunate to have General Mattis in its service once again", said McCain, R-Ariz.
Mattis was beloved by the men and women who served with him. When a reporter addressed him as "General", he responded, "Please call me Jim".