Former Defense Secretary Jim Mattis said on "Fox & Friends" Tuesday that his relationship with President Trump “was not tense,” pushing back on that speculation from host Steve Doocy.

“The president is a forthright man and so am I," General Mattis said.

“I would meet with him weekly. There was nothing going on that I wasn’t open with him about. That’s the way I deal with my boss anywhere I have ever been,” he said.

Mattis, a career Marine who retired as a four-star general in 2013, is promoting his new book "Call Sign Chaos" (co-authored with Bing West), which he said does not reference working in the Trump administration.

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“He [Trump] was elected by the American people,” Mattis said.

Mattis said he came out of retirement to work for the Trump administration. “I was asked to serve and I was raised by the Greatest Generation. But when you’re asked to serve, Republican or Democrat, don’t start wringing your hands asking what to do. Just roll up your sleeves if you’re prepared. Go to work and do your best. It’s very, very simple.”

Among other military matters, Mattis weighed in on the U.S. military’s involvement with Hurricane Dorian. “If FEMA needs them, they’ll be ready.”

He also discussed the terrorist attack on Sept. 11, 2001, after the hosts read an excerpt from his new book that touched on America being able to form allies, despite its history.

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Mattis said that after the 9/11 attack, he listed Canada, United Kingdom, Germany, Norway, Turkey, Jordan, Australia and New Zealand as “allies” who helped us.

“These countries hadn’t been attacked. But their values were attacked. And the values America stands for; I believe you have to go a very long way to find a country more generous in its nature and supportive in those values,” he said.

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Mattis went on to say, “The bottom line is terrorism is an ambient threat. It’s going to be with us. It’s how do we organize with allies to suffocate it is the bottom line. And you can declare war over it. You can want it over. But the enemy gets a vote.”