President Donald Trump’s order to “obliterate” Iranian nuclear-weapons sites just made the whole world a lot safer — not only because he kept a maniacal regime from acquiring nukes, but because other nations must now think twice before defying the United States.

“American deterrence is back,” proclaimed Defense Secretary Pete Hegseth. “When this president speaks, the world should listen” — because the US military “can back it up.”

And, indeed, US military might is a thing to behold.

What a refreshing change from the Obama and Biden years.

Time and again, President Joe Biden issued a toothless, finger-wagging “Don’t” — only for his targets to laugh and do as they pleased anyway, knowing that America’s adversaries would face no real consequences.

“Don’t, don’t, don’t,” Biden threatened any “hostile actor thinking about attacking Israel” after Hamas’ Oct. 7, 2023; Hezbollah and the Houthis struck the Jewish state anyway.

Last year he told Iran “don’t” after it threatened to attack Israel; Tehran responded by launching hundreds of missiles at Israeli targets.

Biden warned Vladimir Putin of “severe consequences” for invading Ukraine; Putin went ahead.

Even after Iranian-backed militants killed three US soldiers and injured 30 others in Jordan last year, Biden’s response was all but nonexistent.

Joe earned the world’s contempt his first year in office with his disastrous Afghan withdrawal, and kept on earning it by repeatedly hesitating in getting Ukraine the arms it needed to do more than slow the Russian onslaught.

President Barack Obama was no better. Recall his “red line” on Syria’s use of chemical weapons? When Bashar al-Assad used them anyway, Obama set off on an elaborate dance to not follow through — even facilitating Moscow’s return to being a Mideast player when Putin offered face-saving cover for Bam’s back-down.

Obama’s answer to Iran’s nukes was to hand the regime billions in exchange for promises to delay gaining them, a deal Tehran quickly violated.

The Obama crew confused America’s enemies with its friends; Biden was just confused — but each opened to door to chaos with bumbling that led to the rise of ISIS and Putin’s first grab of Ukrainian territory on Bam’s watch, then the latest Ukraine war plus the Middle East in flames after Joe took over.

Yes, Trump prefers diplomacy, even to end Iran’s nuclear ambitions.

But he also warned that no deal meant “bombing the likes of which they have never seen before” — and now has proved that his words aren’t empty threats.

And just as Putin, China’s Xi Jinping and other malign actors saw Biden’s Afghan bugout as a US retreat and a license for belligerence, they heard the rumble of Trump’s massive bunker-buster bombs Saturday — and the message they sent about America’s new resolve.

It’s true that Trump strongly prefers peace and is reluctant to use military power, but he’s now proved beyond a doubt that he will use it — and to overwhelming effect — when necessary.

Plus, US deception and strategic misdirection in advance of Saturday’s strikes now make it clear that Trump’s trademark ambiguity is reason for the other guys to worry about what he might do.

America is well-served by that “unpredictability,” even as it was ill-served by Obama and Biden’s predictable weakness.

Bombing Iran’s nuke sites won’t guarantee better behavior from US adversaries, but the Putins and Xis of the world are on notice that they move at high risk of paying a far greater cost than they can afford.

It’s the very definition of deterrence: “Peace through strength” makes the world safer.

Thank goodness the nation has a president who gets it.