WASHINGTON, D.C. (NewsNation) ⁠— A former KGB officer once in charge of Russian President Vladimir Putin says the West should take Putin’s nuclear threats seriously, claiming he’ll “go all the way” to maintain power.

General Oleg Kalugin, 88, spent decades as a Russian spymaster, collecting intel on the U.S. as a former KGB officer. He became the youngest general in the history of the notorious Russian intelligence agency, where he mentored a young Putin and hundreds of other KGB members.

In his 32-year career, Kalugin worked undercover as a journalist while attending New York’s Columbia University as a Fulbright Scholar, conducting espionage and influence operations as a Radio Moscow correspondent with the United Nations. He later would criticize the KGB and Soviet government.

Putin eventually accused Kalugin of spying for the U.S., almost having him arrested and killed before Kalugin found asylum in the U.S.

Kalugin detailed Putin’s rise from his “nobody” subordinate to a “war criminal” in an exclusive interview with NewsNation.

“I remember in St. Petersburg, I was the No. 2 man. (Putin) would come to me, knock on the door, ‘I need my documents signed’ … And that’s all the experience I had with him,” Kalugin said. “He was a nobody.”

Putin went on to rise through the ranks of the KGB and turned on Kalugin — who by that time had transitioned to politics and was a vocal critic of the Soviet Union — branding him a spy for the U.S.

Putin “will try to do all he can to stay in power and, of course, get rid of all potential rivals,” Kalugin said.

Kalugin grew critical of the KGB over time and denounced the Soviet government. Now, he says, Putin is waging a war of his own making.

“Putin actually initiated that invasion of Ukraine. That’s obvious and that’s stupid,” Kalugin said. “Ukraine is a part of … the foundation of the Russian Empire, and to treat Ukrainians as enemies (is) absolutely against all logic, history, everything.”

He doesn’t expect Putin to invade the West, but says the Russian leader is “unpredictable” and that threats of a nuclear attack should not be ignored. A NewsNation/Decision Desk HQ poll released Wednesday revealed that about four in five American voters are concerned about a nuclear attack somewhere in the world within the next decade.

“That’s Putin’s way — to threaten. The western world should not ignore these threats,” he said, adding that Putin “will go all the way just to stop the collapse of the system he has.”

Overall, President Joe Biden has handled Russia’s war in Ukraine the right way, according to Kalugin.

He says what the West is doing is working by isolating Moscow from the rest of the world. Kalugin warned, however, that Putin’s main motivator is power and he isn’t slowing down.”

“He has made his own choices to stay in power as long as he can,” Kalugin said. “He will stay for the rest of his life unless something happens. I don’t envy him. He’s a lonely man.”