Then-president-elect Donald Trump met with Mattis for a little over one hour in Bedminster, New Jersey, on November 20, 2016.
He later wrote on Twitter, "General James 'Mad Dog' Mattis, who is being considered for secretary of defense, was very impressive yesterday.
A true General's General!"
On December 1, 2016, Trump announced at a rally in Cincinnati that he would nominate Mattis for secretary of defense.

As Mattis retired from the military in 2013, his nomination required a waiver of the National Security Act of 1947, which requires a seven-year waiting period before retired military personnel can assume the role of secretary of defense.
Mattis was the second secretary of defense to receive such a waiver, following George Marshall.
The waiver for Mattis passed 81–17 in the Senate, and 268–151 in the House.
Mattis was subsequently confirmed as secretary of defense by a vote of 98–1 in the United States Senate on January 20, 2017.
Senator Kirsten Gillibrand was the sole "no" vote, stating that she was opposed to the waiver on principle.
Then-president-elect Donald Trump met with Mattis for a little over one hour in Bedminster, New Jersey, on November 20, 2016. He later wrote on Twitter, "General James 'Mad Dog' Mattis, who is being considered for secretary of defense, was very impressive yesterday. A true General's General!" On December 1, 2016, Trump announced at a rally in Cincinnati that he would nominate Mattis for secretary of defense.
As Mattis retired from the military in 2013, his nomination required a waiver of the National Security Act of 1947, which requires a seven-year waiting period before retired military personnel can assume the role of secretary of defense. Mattis was the second secretary of defense to receive such a waiver, following George Marshall. The waiver for Mattis passed 81–17 in the Senate, and 268–151 in the House. Mattis was subsequently confirmed as secretary of defense by a vote of 98–1 in the United States Senate on January 20, 2017. Senator Kirsten Gillibrand was the sole "no" vote, stating that she was opposed to the waiver on principle.
Jim Mattis