US President-elect Donald Trump has named Gen James Mattis, a former marine who served in Iraq and Afghanistan, as his defence secretary.
“He’s our best,” Mr Trump said, as he announced his pick in a speech in Ohio.
Gen Mattis, who is known as “Mad Dog”, was an outspoken critic of the Obama administration’s Middle East policy, particularly on Iran.
He has referred to Iran as “the single most enduring threat to stability and peace in the Middle East”.
Mr Trump made the announcement in Cincinnati at the start of a “USA Thank You Tour 2016” for his supporters.
“We are going to appoint ‘Mad Dog’ Mattis as our secretary of defence,” he told the crowd.
“They say he’s the closest thing to General George Patton [World War Two commander] that we have.”
Mr Trump has previously described Gen Mattis, 66, as “a true general’s general”.
The retired Marine Corps officer led an assault battalion during the first Gulf war in 1991 and commanded a task force into southern Afghanistan in 2001.
He also took part in the invasion of Iraq in 2003 and played a key role a year later in the Battle of Fallujah.
Gen Mattis retired in 2013 after serving as the commander of the US Central Command.
Correspondents say his nomination will be popular among US forces.
However, a legal hurdle must be overcome before he can be appointed.
Under US law, a retired officer must be out of uniform for at least seven years before he or she can serve as defence secretary.
Republican-controlled Congress will have to approve legislation bypassing the requirement so he can take up the role.