U.S. President-elect Donald Trump appears with retired Marine Corps General John Kelly outside the main clubhouse after their meeting at Trump National Golf Club in Bedminster, New Jersey on Nov. 20, 2016. Reuters

President-elect Donald Trump has officially added another retired general to his cabinet. Trump announced in a news release Monday that he planned to nominate Gen. John Kelly, former commander of the United States Southern Command and Marine Corps veteran, to be secretary of the Department of Homeland Security.

"He is the right person to spearhead the urgent mission of stopping illegal immigration and securing our borders, streamlining TSA and improving coordination between our intelligence and law enforcement agencies," Trump said in the release. "With Gen. Kelly at the helm of DHS, the American people will have a leader committed to our safety as well as one who will work hand-in-hand with America's rank-and-file TSA, ICE and Border Patrol officers."

Kelly's name had been floating for days before the formal announcement. Other candidates on Trump's list reportedly included Rep. Michael McCaul, R-Texas, and Frances Townsend, who served as President George W. Bush's homeland security adviser.

Here's what you need to know about him:

1. Kelly joined the Marine Corps in 1970, and he served time in Mayport, Florida; Camp Pendleton, California; Mons, Belgium; and Iraq throughout his 40 years in the military, according to his profile on the Department of Defense website.

2. He became a Gold Star father in 2010 when his son Robert died in Afghanistan.

3. More recently, the general oversaw the prison at Guantánamo Bay and advocated for increased border security, the New York Times reported.

4. Kelly has worked closely with current Department of Homeland Security secretary Jeh Johnson, former CIA director Leon Panetta and former defense secretary Robert Gates.

5. He has often voiced concerns about threats from countries in the Middle East and Latin America in congressional testimony.

"Unless confronted by an immediate, visible, or uncomfortable crisis our nation's tendency is to take the security of the Western Hemisphere for granted," Kelly said in 2015, according to the Military Times. "I believe this is a mistake."

6. If confirmed, Kelly would likely take on projects like Trump's promised wall along the border with Mexico, advocate for human rights and strengthen the U.S. Immigration and Customs Enforcement team, the Washington Post reported.

7. He said he's "humbled" to be Trump's pick.

"The American people voted in this election to stop terrorism, take back sovereignty at our borders and put a stop to political correctness that for too long has dictated our approach to national security," Kelly said in the release announcing his nomination. "I will tackle those issues with a seriousness of purpose and a deep respect for our laws and Constitution. I am honored for the opportunity to be back in the service to our country, and our people."