Years ago, Henry Kissinger wisely observed that Iran had to decide “whether it wants to be a nation or a cause.”

Kissinger made that comment in 2006, and in the years since, Iran’s leaders have made their choice bloody obvious: Iran is a cause, and that cause is spreading a violent Shia revolution throughout the Mideast and across the world.

In making the decision to commit murder and mayhem abroad while oppressing their own people, the ruling mullahs sealed their fate with President Trump. Instead of using the sanctions relief they gained under the deal President Barack Obama negotiated to expand their economy and human rights at home, they used their cash windfall to develop a ballistic-missile program and spread terrorism throughout the region.

They daily threaten Israel with destruction and put proxy armies on Israel’s borders with Syria and Lebanon. They are trying to put Saudi Arabia in a similar vise by arming rebels in Yemen.

These and other aggressive actions made Trump’s decision an easy one.

In fact, nuking the nuke deal wasn’t just the best course. It was the only responsible and realistic course.

That’s not to say the president’s decision is risk-free. That option does not exist. But sometimes, and this is one of those times, the status quo is more dangerous than dramatic change.

As the president said, he is withdrawing from the pact not just because the terms are terrible, which they are. It’s also because the deal is too narrow and because Iran’s malignant behavior has actually gotten worse.

“This was a horrible, one-sided deal that should have never, ever been made,” Trump said in his forceful remarks. “It didn’t bring calm, it didn’t bring peace, and it never will.”

He called the sunset provisions of up to 15 years “unacceptable” and added, “If I allowed this deal to stand, there would soon be a nuclear-arms race in the Middle East. Everyone would want their weapons ready by the time Iran had theirs.”

That is just one of the under­appreciated flaws of the deal. Long before the terms expired, the prospect of Iran getting nukes would have triggered others in the region to get one first. And so instead of restraining Iran, the deal more likely would have sparked a nuclear-arms race.

More broadly, Trump’s action is yet another reminder that he is not beholden to the conventional wisdom of American liberals and European appeasers.

They all convinced themselves that by welcoming Iran back into the international economic system, the mullahs would moderate their behavior for the good of their own people.

That assumption was at best foolishly naive.

It was also, truth be told, driven in large part by the desires of European and American businesses to sell their wares to Iranians.

But the deal’s advocates should have learned from the violent suppression of Iranians who demonstrated against the regime in 2009 that the mullahs cared only about retaining power and spreading the revolution that began in 1979 with the overthrow of the shah and the seizing of American hostages.

If the mullahs and their henchmen were willing to kill and torture thousands of their own citizens for daring to criticize them, what was the basis for assuming they suddenly would become peaceful members of the international community?

Trump’s decision, which keeps faith with a campaign promise, predictably infuriated the usual critics. To their discredit, they trotted out a parade of horribles while neglecting to address Iran’s behavior and its unwillingness to negotiate major changes to the pact.

Stripped of exaggerations, the critics’ warnings are based largely on a desire to avoid confrontation now at any price, the future be damned.

That approach might make some sense if Iran were a normal country. But its actions since the overly-generous 2015 deal show that it remains a gangster regime fixated on regional domination. Its goals are not compatible with international norms, so blocking its access to the global banking and trading networks is the only peaceful recourse.

And as Trump stressed, the military option is still available. If Iran races to build a bomb, he warned, “it will have bigger problems than it has ever had before.”

The president also made two other key points that addressed the concerns of some critics, especially those of European leaders. First, he left open the possibility of making a new, improved deal and said he believed Iran’s leaders eventually would come to that conclusion. When they do, he promised, they would find him, “ready, willing and able” to negotiate.

He also turned on its head the argument by some, especially on the American left, that withdrawing from this deal would make it more difficult to achieve a breakthrough with North Korea.

The president said the doubters have it exactly backward, insisting that his actions send a “critical message” to others who question his resolve and would make North Korea more likely to give up its nukes.

“The United States no longer makes empty threats. When I make promises, I keep them,” Trump said. He then announced that Secretary of State Mike Pompeo was on his way to North Korea to finalize negotiations involving the president’s historic meeting with Kim Jong-un.

As I wrote Sunday, Trump’s approach to national security leverages America’s strengths instead of being paralyzed by potential pitfalls. He is not, like his predecessor, “leading from behind” or doing nothing under the guise of “strategic patience.”

Instead, he is proving to be the same bold disrupter on the international stage that he is in domestic politics.

Next week will bring another example, when Trump moves the American Embassy in Israel to Jerusalem.

Presidents for decades promised to do it, but all found excuses for delay.

Once again, Trump is keeping his word.

On one level, the embassy move is purely symbolic. But on another, it also sends the same powerful message to the world he sent Tuesday:

We stick with our friends, and we stick it to those who would do us harm.