Author and retired Lt. Col. Alexander Vindman discusses his new book, "The Folly of Realism: How the West Deceived Itself About Russia and Betrayed Ukraine," and addresses President Donald Trump's approach to ending Ukraine's war with Russia.

During the first Trump administration, Vindman was the director for European Affairs on the National Security Council.

Vindman also became known as the whistleblower who raised concerns about Trump's July 2019 phone call with Ukrainian President Volodymyr Zelenskyy, which sparked an impeachment inquiry. He testified that Trump pressured the Ukrainian government to investigate the family of Joe Biden -- who was then Trump's political rival. After a months-long impeachment and Senate trial, Trump was acquitted in 2020.

ABC News' Phil Lipof sat down with Vindman to discuss his book, Trump's strategy in dealing with the war and his overall predictions for the president's second term.

ABC NEWS: This week marks three years since Russia invaded Ukraine. President Trump now calling Ukrainian President Zelensky a dictator, later blaming Ukraine's leaders for Putin's attack on that country. It has obviously sparked controversy.

To discuss this change in policy from the Trump administration, and Russia, and the possible end of the war in Ukraine, is author, retired lieutenant colonel and former Trump staffer Alexander Vindman.

With his newest release, you see it there on the screen, "The Folly of Realism: How the West Deceived Itself About Russia and Betrayed Ukraine."

Alexander Vindman, thanks so much for coming in to talk about this. Let's start with where we find ourselves today. The newest Trump administration and the shocking vote that happened this week at the UN, the U.S. siding with North Korea in that vote. What do you make of this?

VINDMAN: It's how the U.S. deceived itself about Russia.

ABC NEWS: That's the title of your book, yes.

VINDMAN: I mean, you know, honestly, it's a very serious topic, but that's the first thing that comes to mind. The reason that I wrote this book is I want to understand how we got to this war in the first place.

And there's a fair bit of continuity between the mistakes that were made in the past and the mistakes that Trump is making now, in that we put Russia first consistently over the past 30 years.

This is a whole, what's shocking to us now is that it's at a different level. It's like the the end stage -- the, you know, poison Kool-Aid stage of the folly of realism and all these mistakes we're taking just being magnified in Trump in the way he does things excessively.

So taking this position where he's siding with Russia, siding with North Korea, siding with our traditional adversaries, as opposed to with our traditional allies, the Europeans, Ukraine -- that is a shock to the system. But there is also too much continuity with the mistakes of the past.

ABC NEWS: I want to talk about the mistakes of the past because you say this goes beyond one administration to the next, even beyond political parties. But just today, Trump said Russia will need to make some concessions in order for this war to end. That's new. He's been focused on Zelenskyy. What do you think both sides are going to have to do to make this end?

VINDMAN: Well, I think the fact is that it's crystal clear to me that the Ukrainians will bend over backwards to compromise. They want an end to this war, but they're not going to do so in a way that completely compromises their sovereignty, national security or territorial integrity.

If they, the maximum position in that kind of compromise would be something that provides guarantees so that Russia doesn't engage. The challenge here is not the Ukrainians, that are willing to accommodate and really want peace. It's the Russians that are completely inflexible and want capitulation.

ABC NEWS: You talk a lot about your military, your career and your time as a military officer serving under Trump's previous administration. You, of course, are Ukrainian-American. You also say Trump's appeasement of Russia won't end with the Ukraine war. What do you mean by that? 

VINDMAN: I think the fact is that until we make a decisive shift away from this realism, this idea that countries only pursue their national interests exclusively and maximally and everything is a transaction -- we need to get the best deal out of each engagement.

We start to focus on the long term. This idea of neo-idealism I talk about, when we start to think about what really matters to us. It's stability. It's the friendships we have with our allies that give us economic prosperity, give us the security that we need when we're attacked like we were in 9/11. Until we make that change to a different approach, we're going to keep repeating the same mistakes over and over.

ABC NEWS: Taking a step back. What can truly be done to mitigate the sense of what you have called the ongoing fractured global order? 

VINDMAN: This is, I think right now we're in this phase of we could expect four years of Trump. We're going to have to weather that storm to a certain extent, a lot of unpredictability, a lot of chaos, a lot of public pronouncements that then get moderated in reality and execution.

We'll see that play out repeatedly. It happened in the first administration. It'll happen in this administration. I think our friends will find us less reliant, and they're going to have to go it alone to a certain extent. They're going to double down, let's say, for instance, on support to Ukraine, maybe even put troops on the ground in Ukraine.

ABC NEWS: We're already hearing some of that from Europe.

VINDMAN: But there will be a time where we're past Trumpism. The pendulum has swung so far over to this extreme state. It's going to normalize.

ABC NEWS: Alexander Vindman, thank you so much. Do appreciate it. And you can now purchase the "The Folly of Realism: How the West deceived itself about Russia and betrayed Ukraine," wherever books are sold.