NEW YORK -  President-elect Donald Trump announced Thursday that he has selected James Mattis, who has said that responding to “political Islam” is the major security issue facing the United States, to lead the Defence Department.

"We are going to appoint 'Mad Dog' Mattis as our Secretary of Defence," Trump told a political rally Thursday night in Cincinnati, Ohio.

 Mattis, a retired Marine general, earned his 'Mad Dog' nickname “after the 2004 battle of Fallujah in Iraq, where he led British and American troops against Iraqi insurgents.

Mattis retired in 2013 after leading the military’s Central Command, which oversees military operations in the Middle East and Africa. He will require a waiver from Congress to become Defence secretary because the law prohibits veterans who have been retired for fewer than seven years from taking the job. That is expected to be a formality, given support for him from many in Congress, including Republican Senator John McCain, ,\ the influential chairman of the Armed Services Committee.

Mattis made headlines at a series of prominent commands with blunt talk that appealed to troops and left no doubt about his approach to war. After leading troops in combat in Iraq and Afghanistan, he told an audience in San Diego in 2005 that he relished fighting.

"Actually it's quite fun to fight them, you know. It's a hell of a hoot," Mattis said. "It's fun to shoot some people. I'll be right up there with you. I like brawling. 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."

Those remarks earned him a rebuke from his superiors but didn’t stop his ascent to the military’s most prestigious and taxing posts. Known as the “Warrior Monk,” Mattis also cultivates a bookish reputation.

Mattis is a visiting fellow at the Hoover Institution at Stanford University, and has continued to speak out about military policy in retirement. In 2014, he criticized the Obama administration’s plan to withdraw all US troops from Afghanistan at the end of 2016, a stand that it has abandoned in favour of leaving about 10,000 troops there to train local forces and fight terrorists. Deadlines for withdrawal, Mattis said then, simply embolden American enemies.

“We want to crush the enemy’s hope to w through violence,” Mattis said. “Yet we have now given the enemy hope that if they hang on until our announced withdrawal date they can perhaps come back.”

Mattis’ views may mesh with Trump’s calls to beef up the military and more aggressively prosecute the war against Islamic State terrorists.

As Defence secretary , Mattis will inherit the ongoing air war in Iraq and Syria, as well as the thousands of US troops on the ground there who training local forces and elite commandos who are targeting leaders of the terrorist organization, also known as ISIL. The war against Taliban insurgents and al Qaeda-linked terrorists in Afghanistan will grind on as well.

He’ll be responsible for more than 1 million active-duty troops and a budget of more than $600 billion annually.