At a Cincinnati post-election victory rally Thursday, president-elect Donald Trump announced retired Gen. James “Mad Dog” Mattis as his choice for Defense Secretary. Mattis is Trump’s latest pick, along with Steve Bannon, who Trump picked for Chief Strategist and Senior Counselor, as well as South Carolina’s Gov. Nikki Haley, Trump’s pick for U.N. Ambassador.

"We are going to appoint 'Mad Dog' Mattis as our secretary of defense. But we're not announcing it until Monday so don't tell anybody," Trump said at his rally. Mattis is a retired 66-year-old Marine Corps. general. He retired in 2013 after he served as commander of the U.S. Central Command from 2010 to 2013, leading war efforts in Iraq and Afghanistan.  

In order for Mattis to be approved for the position, the Associated Press noted, Congress would have to bypass the law which prohibits retired “military officers from becoming defense secretary within seven years of leaving active duty.”

Trump’s pick has already gotten opposition from Sen. Kirsten Gillibrand, member of the Senate Armed Services Committee Subcommittee on Personnel. Gillibrand released a statement Thursday.

While I respect Gen Mattis’s service, I'll oppose a waiver-civilian control of our military is a fundamental principle of American democracy

— Kirsten Gillibrand (@SenGillibrand) December 2, 2016

Mattis did, however, receive support from fellow serviceman and Chairman of the Senate Armed Services Committee Sen. John McCain. “I am pleased that the President-elect has selected General James Mattis to be his nominee for Secretary of Defense,” McCain said in a statement. “As Chairman of the Senate Armed Services Committee, I look forward to moving forward with the confirmation process as soon as possible in the new Congress. I have had the privilege of knowing General Mattis for many years. He is without a doubt one of the finest military officers of his generation and an extraordinary leader who inspires a rare and special admiration of his troops. General Mattis has a clear understanding of the many challenges facing the Department of Defense, the U.S. military, and our national security. America will be fortunate to have General Mattis in its service once again.”

Mattis has been involved in controversies, including over his remarks in 2005 at a San Diego forum where he said, "Actually, it's a lot of fun to fight. You know, it's a hell of a hoot. ... It's fun to shoot some people. I'll be right up front with you, I like brawling." He added, "You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil. You know, guys like that ain't got no manhood left anyway. So it's a hell of a lot of fun to shoot them." The following year, Mattis was at the center of another controversy when 24 Iraqi unarmed women and children were killed by four Marines. Mattis dismissed charges of unpremeditated murder on the four Marines and dropped charges on another four officers who were accused of not reporting or investigating the civilian deaths.