Chuck Hagel believes we have entered "a defining year, a year of volatility and uncertainty and great danger" for the United States and the world.
A year that will determine whether America continues to "walk away from its indispensable leadership position" in the world.
A year when Republicans in Congress may be called upon to choose country over party.
A "rather significant political year" when voters will shape the next Congress.
"We have not really seen these kind of times since Watergate and Vietnam," Nebraska's former U.S. senator and the former U.S. secretary of defense said during a wide-ranging telephone interview from Washington.
While President Donald Trump is at the heart of all this, "intentionally dividing the country and the world," pulling away from alliances that have benefited America and abandoning trade agreements that have been in U.S. interests, he is not the only catalyst in play, Hagel said.
"Globally, you see the same political dysfunction in virtually every democracy in the world," Hagel said, with England abandoning the European Union, German Chancellor Angela Merkel struggling to form a coalition government and Emmanuel Macron bringing a new face to the government of France.
"Nationalism, populism everywhere," Hagel said.
As for Trump himself, Hagel emailed a blunt assessment one day following the interview after the president asked congressional leaders why the United States should be open and welcoming to immigrants from "sh**hole countries" like Haiti and in Africa.
"Donald Trump is doing great damage to our country internationally," Hagel said. "He's an embarrassment."
Hagel, who served two terms in the Senate, said his fellow Republicans may face a moment of truth later this year with the investigation of Russian influence and interference in the 2016 presidential election already probing inside the doors of the Republican White House.
"We take an oath of office not to a president, not to a party, not to a philosophy, but to the Constitution of the United States," he said.
"I was philosophically a Republican with a conservative voting record," Hagel said, "but that did not mean I would always go along with the party.
"In the end, you need to make a decision based on the right thing for the country," he said.
Hagel, who was wounded twice in combat in Vietnam, parted company with Republican President George W. Bush on the Iraq war and was widely criticized within the GOP for his action with Vice President Dick Cheney often acting as one of Hagel's sharpest critics.
As secretary of defense, Hagel said, he saw Russian cyber activity in all areas of the U.S. economy, with attempts to penetrate commercial and financial networks as well as the Department of Defense.
"The Russians were up to a lot of mischief," he said. "They were probing and they do have the capability of getting better and stronger. We can't discount that."
Hagel left the Pentagon in 2015, a year before the presidential election.
Now, Hagel said, the country has "a president who minimizes his own intelligence community and that is quite astounding."
Touching on other topics, Hagel said he believes the United States should initiate talks with North Korea about its growing nuclear military threat.
"Engagement is not surrender," he said. "Great Powers are not afraid of talking to people and it's up to us to take the first step.
"Dialogue is the only responsible way forward," he said. "We have to sit down and try to work our way through this. And I don't think you can expect any kind of engagement by demanding preconditions."
"'My button is bigger than yours' is irresponsible kind of talk," Hagel said, referring to a tweet that Trump aimed at North Korean leader Kim Jong-un.
A nuclear confrontation would be "worse than anything we've ever seen," Hagel said.
Millions of people, including tens of thousands of Americans, could be killed in North Korea and South Korea alone, he said.
On other topics, Hagel said the Trump administration's withdrawal from the Trans-Pacific Partnership trade agreement did "significant damage" to long-term U.S. power and influence in Asia while damaging the interests of U.S. farmers and ranchers.
"It allowed the Chinese to fill that vacuum; it was like a gift. And that is permanent and very damaging."
The administration's threat to the North American Free Trade Agreement also poses a potential blow to U.S. agriculture, he said.
"I'm surprised that our Midwestern Republican leaders have not been more vocal about that," Hagel said.
Current U.S. foreign policy is "a policy of disunity," he said.
"A new world order is being built and shaped right now and the last time that happened, America led."