The calendar turns and a decade begins, but there is nothing new under the sun in Washington. Even the killing of an Iranian mass murderer is cause for more partisan strife.

In a sane country, which America used to be, there would be shared sober satisfaction over the elimination of Gen. Qassem Soleimani. Yet Democrats apparently outsourced their reactions to robots, whose script called for conceding that the departed was a very bad man, but prohibited approval of President Trump’s decision to take him out.

Instead, the quibblers’ chorus raised questions of timing and expressed fear of escalation and retaliation. In the context of Iran’s military aggression and Soleimani’s bloody hands, there is another word for that fear: appeasement.

Or, as defense specialist Michael Doran wrote in The New York Times, the fear of war “ignores the fact that Mr. Soleimani has been waging war on America and its allies for years.”

The latest example was the attack on our embassy in Baghdad, carried out by groups allied with Iran. That is the sort of dirty work Soleimani specialized in — getting Arab Muslim proxies to fight and die for Iran’s goal of regional dominance.

In addition to Iraq, where Iranian munitions he provided killed or maimed thousands of American soldiers, Soleimani forged terror groups in Lebanon, Syria and Yemen. He was hailed as a martyr by Hamas in Gaza, leading Israel to warn it and another Iran-backed group, Islamic Jihad, against retaliation.

The notion that Trump was wrong to act, if followed to its logical conclusion, means America should play only a tit-for-tat game with terrorists everywhere and all the time. This is the same screwy thinking that demands Israel hit its enemies only as hard as the enemies hit it.

What is the point of having a superior military force if it can’t be used to defend its homeland and citizens?

The criticism also shows Dems still haven’t figured out Trump. The self-proclaimed king of counterpunching has never been content to trade glancing blows. “If you hit me, I’ll hit back, 10 times harder,” he has said.

Unfortunately, a counsel of timidity is now virtually the only voice heard on the left. Peace-through-strength advocates are as plentiful as hen’s teeth in the modern Democratic Party, and that was true even before the birth of the hate-Trump phenomenon of the last three years.

President Barack Obama’s global apology tours shattered historic norms and his attempts to appease Iran’s mad mullahs broke new ground in the worst possible way. Iran took his concessions — and stacks of American cash — and used them to foment even more mayhem against our allies, including Saudi Arabia and Israel.

Soleimani was the spearhead of this violent expansion, and it is noteworthy that both Obama and his predecessor, President George W. Bush, passed up opportunities to drone him, fearing the backlash.

Trump, too, was patient, even as he shifted our Iran policy 180 degrees by exiting Obama’s misbegotten nuclear deal and using tough economic sanctions to try to force the regime to mend its ways. But his offers to meet were met with threats, the slaughter of Iranian dissidents, repeated attacks on our allies and, finally, our Baghdad embassy.

Naturally, the president’s decision that enough was enough led the celebrity sewer to open its mouth, with Rob Reiner, Debra Messing, Rose McGowan and others sputtering foul nonsense. Rosanna Arquette went straight to the Hitler comparison. Ho hum.

The vapid comments reveal that the Soleimani targeting is triggering the same strain of derangement that fueled impeachment. If you hate Trump, every event is just grist for the effort to tear him down.

Whatever he says or does must be mocked and resisted. Don’t let facts or even national security get in the way of your moral preening.

Former Veep Joe Biden, who famously said he opposed the raid that dispatched Osama bin Laden, hasn’t learned anything. He said Trump “just tossed a stick of dynamite into a tinderbox” and warned that “we could be on the brink of a major conflict across the Middle East.”

Sen. Elizabeth Warren called the killing of Soleimani “reckless” and said “our priority must be to avoid another costly war.”

Their approach makes a virtue of weakness and invites further attacks. Of course we should try to avoid war, but passivity in the face of evil has never yielded a durable peace.

Even the most plausible Dem criticism — that Trump acted without congressional approval — fails the test of common sense. Should he have called for a public vote? Should he have trusted Speaker Nancy Pelosi and Rep. Adam Schiff to keep the mission secret?

The bitter acrimony Dems created with their impeachment jihad left Trump no practical alternative to a secret raid. Especially when, as Secretary of State Mike Pompeo said, Soleimani was preparing to launch more attacks on Americans. That’s presumably why he was in Baghdad and meeting with a cabal of evildoers, all of whom died with him.

The fact is that Soleimani deserved to meet his maker years ago but would be alive had he heeded warnings to stop spreading terror throughout the Middle East. He didn’t and there should be no mourning in America over his death.

None of this is to deny there are risks associated with such a dramatic mission. The mullahs will feel the need to avenge a key leader, with Ayatollah Ali Khamenei warning the US that “harsh revenge awaits the criminals.”

Such dire talk notwithstanding, some analysts believe Iran will not risk all-out war with the US but will more likely initiate smaller incidents that gain attention without provoking a crushing American response. If nothing else, the last 40 years reveal that Iran’s Islamic rulers are big on other people becoming martyrs but show remarkable restraint when their lives are at stake.

Trump addressed those issues and more in his clear and forceful remarks Friday. Like his best speeches, it was relatively brief, lasting about five minutes, and skipped soaring oratory in favor of plain talk that spelled out his policy and red lines.

Although nearly 3,000 more American soldiers are being sent to the region, the president said he favors de-escalation, declaring, “We took action last night to stop a war, we did not take action to start a war.”

He repeated his promise that the US is not seeking regime change, but urged Iran to end its “aggression.” He also warned it would pay a heavy price for any retaliation, saying, “If Americans anywhere are threatened, we have all of those targets already fully identified, and I am ready and prepared to take whatever action is necessary.”

That is what peace through strength sounds like. Democrats and the mullahs would be wise to pay attention.