The world order is under attack, and NATO is essential to peace, Ret. Gen. James "Mad Dog" Mattis said Thursday at his Senate confirmation hearing to be Donald Trump's pick for Defense secretary.
"I think it's under the biggest attack since World War II, sir, and that's from Russia, from terrorist groups and with what China is doing in the South China Sea," Mattis said in answer to a question from Sen. John McCain.
McCain, chairman of the Senate Armed Services Committee, also asked Mattis if he thought there were lessons to be learned from history in dealing with Russian President Vladimir Putin.
"Chairman, history is not a straitjacket, but I've never found a better guide for the way ahead than studying the history. Since Yalta, we have a long list of times that we've tried to engage positively with Russia. We have a relatively short list of successes in that regard," the retired Marine general said.
Mattis emphasized the importance of recognizing "the reality of what we deal with" in regards to Russia and its president, who the retired general says is trying to "break" the North Atlantic Treaty Organization alliance. He said that the U.S. must take "integrated steps" involving diplomatic, economic and military actions to "defend ourselves." But international alliances are essential to American success, Mattis said in his opening remarks.
"In addition to ensuring collaboration across government and the adoption of an integrated strategy, we must also embrace our international alliances and security partnerships. History is clear: Nations with strong allies thrive and those without them wither," he said.
In line with his opening comments, Trump's Defense secretary pick broke with the president-elect when discussing the NATO. On the campaign trail, Trump called NATO "obsolete" and claimed it wasn't doing enough on the terrorism front. But Mattis called it "the most successful military alliance, probably, in modern world history, maybe ever."
"I would see us maintaining the strongest possible relationship with NATO," he said.
Despite the apparent differences, Mattis said he's discussed the matter with Trump. He said the president-elect has been open-minded and understands what his position is on NATO and other issues.
Mattis, 66, is widely expected to be confirmed. In December, news of Trump's intention to pick him for Defense secretary was commended by many, including McCain, R-Ariz.
"He is without a doubt one of the finest military officers of his generation and an extraordinary leader who inspires a rare and special admiration of his troops," McCain said in a December statement.
One potential hiccup for Mattis is the cancellation of his scheduled Thursday appearance before a House Armed Services Committee hearing on the issue of civilian control of the military. A Democratic spokesperson for the committee said, "this is not a minor issue. This is a major issue affecting the principle of civilian control of the military."
A 1947 law stipulates that service members must be out of uniform for at least seven years before serving as Pentagon chief. Mattis retired from his role as head of U.S. Central Command in January 2013 and would need a waiver from Congress to serve as Defense secretary.
In his prepared statement, the retired general acknowledged that the role of Defense secretary would be markedly different from his career as a military officer. He expressed respect for the tradition of civilian control, calling it a "fundamental tenet of the American military tradition."
"Civilian leaders bear these responsibilities because the esprit-de-corps of our military, its can-do spirit, and its obedience to civilian leadership reduces the inclination and power of the military to oppose a policy it is ultimately ordered to implement," Mattis said.
The retired general has served in the Vietnam War, the first Gulf War, Iraq and Afghanistan. He earned his nickname "Mad Dog" for his blunt, tough-talking manner.
"Be polite, be professional, but have a plan to kill everybody you meet," he was once quoted as telling Marines in Iraq.
— CNBC's Jeff Daniels and NBC News contributed to this report.