When I recently asked a North Korean defector, who I have known for years, how he would describe dictator Kim Jong Un to President Trump as he prepares for his summit—or showdown—in Singapore, an instantaneous, one-word answer was all that was needed.

“Hitler.”

I paused, partly out of shock, but partly out of anger, as my own family was forced to leave Greece after World War II, all thanks to the countless horrors inflicted by Nazi Germany.

I wanted to ask my friend why he offered such a brief but unsettling answer—attempting to point out what that meant, the severity of such a statement and how it seemed sometimes almost overused, to the point of being nearly worthless.

But I never got the chance.

Knowing him all too well, I could tell he was growing impatient. He cut me off, something he has never done, his tone shifting all so slightly, as if I had awakened something inside of him.

He explained that “[W]e should not be fooled. The Kim family is as if Hitler had children—a three-generation Hitler dynasty—all ruling over my people for seven decades. They have killed millions of us [Koreans], starved us, broken up our families, forced millions to live in poverty or concentration camps, all the while building terrible weapons that can kill millions of people. Who else should I compare the Kim’s to?”

Checkmate.

History tells us all the photos and summits in the world won’t stop a dictator bent on survival or geopolitical ambitions counter to our own.

The phoneline then went quiet. I thought maybe we lost the connection. I thought I might have pushed too far. But after a few seconds, he would speak again. While not one to scream or even show emotion—Kim’s thugs beat that out of him thanks to torture sessions he described to me that can only be described as crimes against humanity—I could feel pain mixing with anger, even thousands of miles away, that was buried deep down, crying to come out.

While the words would come, there was a pulsing delivery attached to them, as if primitive human language could never convey the pieces the Kim regime had chipped away from his soul, or the anger that wrapped around him, like a blanket of terror, that he could never shake off.

“Kim starts crisis after crisis, just like Hitler, only to ask for talks, and peace or concessions. The Kims are the Korean people’s Hitler. That is what I would tell Mr. Trump.”

Before asking to move on from this subject, he added one thing, predicting what North Korea will do in Singapore: “Kim will lie, agree, shake hands—do whatever he can to wash away his family’s sins. And then, just when you think he is respectable, a so-called world leader, he will cheat you again. Just like Hitler.”

And history tells us he very well could be right.

Perhaps only someone touched by the terror that is the Kim regime could provide the only actionable advice to the leader of the free world: trusting a tyrant is a fool’s errand.

And yet, President Trump will have to do just that.

The good news, as if there is any when a democratically elected head of state is forced to sit down with the leader of a rogue regime—whose reign was forged in blood—is that many democracies, including our own, have a long past of negotiating with leaders like Kim, sometimes proving historic and meaningful, while other times resulting in disaster.

For example, Britain’s Neville Chamberlain thought he had forged “peace in our time” with Hitler.

Then, there is the example of President Franklin Roosevelt, who allied with the Soviet Union’s Joseph Stalin to defeat Nazi Germany during World War II.

Then there is Nixon, who, in an effort to strengthen what looked at the time like declining U.S. power after Vietnam, opened relations with Maoist China, a dictator responsible for the deaths of countless millions—including Americans.

Even today, Washington has relations with countless nations that have horrific human rights records, terrorize their own people and treat freedom as if it was a prize to be locked away—something to be feared instead of cherished.

But history tells us something else about dealing with tyrants, as the North Korean defector points out almost too well: they often lie to get what they want. And the price for falling for their lies is often high.

Chamberlain, in his rush to secure the peace, ended up setting events in motion that in hindsight guaranteed a second world war—with mankind paying the ultimate price for appeasing evil.

While FDR would win that war with Stalin at his side, Moscow would go on to enslave Eastern Europe with the Soviet leader completely disregarding his commitments at the Yalta summit.

And Maoist China, thanks to Nixon’s opening, would indeed join the international community—proving a worthy partner against the USSR. However, the Chinese people to this day have never tasted freedom. While they have become rich, it has come at the highest of prices: the complete control of their society by the Chinese Communist Party, who is looking more and more like an enemy of America with each passing day.

While I can only pray that President Trump can somehow find the magic formula to convince North Korea to give up its nuclear weapons and join the international community, knowing that there is a brighter future at the end of such a process, history and experience tells us no dictator with the devilish DNA of Kim Jong Un is easily transformed, if ever.

My own prediction for Singapore, therefore, is an easy one: the history books tell us the pictures will be momentous, the handshakes memorable and the hope for a better future inspiring. A nuclear deal is even possible.

But history cries out for caution, skepticism and the constant testing of North Korea’s intentions.

As is most likely the case, Kim will never keep his word, trying to draw us into years of negotiations, all the while building more nuclear weapons and better missiles. History shows us that is Pyongyang’s preferred playbook, and it works all too well to change tack now.

History also tells us all the photos and summits in the world won’t stop a dictator bent on survival or geopolitical ambitions counter to our own. Only our resolve—and the courage to face down evil when we see it, to confront it as it is, contain it and fight against it if we must—will ever win the day.

And we all know what happens when we don’t listen to history—or to those who have been impacted by it.