President-elect Donald Trump has picked Gen John Kelly to head the Department of Homeland Security.

Gen Kelly, 66, is the third military general appointed by Mr Trump to a post in his Cabinet. He previously named Lt Gen Michael Flynn to be his national security advisor. Retired Gen James Mattis accepted the offer to be Defence Secretary, pending a congressional waiver since he only retired three years ago.

CBS News reports that Gen Kelly, a retired Marine, was travelling to Europe when the Trump transition team made the offer, which he accepted while abroad. An announcement of the formal offer is expected next week.

Gen Kelly has served almost five decades in the US Marine Corps. He was the commander of US Southern Command – which is responsible for all military activities in Central and South America. He also commanded US forces in Iraq, before serving as an aide to defence secretaries Leon Panetta and Robert Gates.

Gen Kelly became the highest ranking member of the military to lose a child in combat. In 2010, Lt Robert Michael Kelly died after stepping on a landmine in Afghanistan.

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The New York Times said the loss played a role in Mr Trump’s decision to bring on the general.

While with the US Southern Command, Gen Kelly oversaw the military prison at Guantanamo Bay in Cuba. Human rights activists have rebuked the US government for the treatment of prisoners on the base – which included force-feeding prisoners who staged hunger strikes. Gen Kelly rejected such criticism.

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“Human rights groups on the one hand will criticise the US government for enteral feeding,” he said in 2014. “But in private, they’ll tell me, ‘Thank goodness you’re doing this. These people might hurt themselves’.”

“I am charged by the president, we are charged by the president – the US government – to maintain their health to the degree that we can,” he continued. “They have, frankly, better healthcare down there than probably the veterans in our country have, and they certainly have as good of health care down there as anyone in the US military does.”

Gen Kelly was also critical of the Obama administration upon the announcement that it would open up combat roles for women in the military. He was against the idea, saying that the armed forces would have to lower their standards to include women in the frontlines.

“There will be great pressure, whether it’s 12 months from now, four years from now, because the question will be asked whether we’ve let women into these other roles, why aren’t they staying in those other roles?” he told reporters in January.