It was a day like no other. A beautiful September morning transformed into horror and death, with nearly 3,000 innocents murdered for the crime of living and working in America.

We promised ourselves and each other we would never forget. Memorials to the heroic firefighters invariably echo that defiant pledge: Never Forget.

They lie. Not 15 years later, many Americans are forgetting. Even in New York, people who solemnly swore to remember forever turn their backs on the meaning of September 11th.

The pledge was the only way to make sense of the gruesome deaths of so many. The burning towers, people jumping and falling, the twin collapses and the clouds of smoke and steel and flesh and survivors covered in chalky, choking dust. Then came the fires and that awful smell that wouldn’t go away.

In unity, we made the vow even as we feared other attacks. We were wounded but determined to triumph because that’s what Americans always did.

We also pledged because, like earlier patriots, we were eyewitnesses to evil. We saw its soulless savagery and knew they would kill us all if they could.

Perhaps it was inevitable that such charged emotions would dull. The Long War has been a hard war, and it is difficult to sustain the commitment for 15 years.

But there is something else at work, too. The forgetting in some circles is intentional. As determined as many still are to Never Forget, others are determined to move on, to redefine, to downplay.

None is more consequential than Barack Obama, a dedicated re-interpreter of 9/11 and its aftermath. As his presidency enters the home stretch, we see the full flowering of his wrongheaded determination.

His angry scolding of those who insist on using the term “radical Islam” for our enemies and his effort to minimize the role of Islamist ideology in the slaughter in Orlando are shocking — and yet entirely consistent with his worldview.

Estranged in important ways from both mainstream America after 9/11 and modern Islam, the president nonetheless sees himself as a bridge between the two. He gave himself that assignment in his 2009 Cairo speech, citing his father’s Islamic background in Kenya and his own boyhood in Indonesia.

“I consider it part of my responsibility as president of the United States to fight against negative stereotypes of Islam wherever they appear,” he declared. “But that same principle must apply to Muslim perceptions of America. Just as Muslims do not fit a crude stereotype, America is not the crude stereotype of a self-interested empire.”

That aim, surely born of good intentions, was a profound mistake that continues to wreak havoc. The president of the United States cannot be a broker between his countrymen and a foreign enemy that has declared war on us.

As commander in chief, his job is to lead this nation to victory. He hasn’t because he refuses to see it as a war.

As the late Fouad Ajami wrote, Obama sees himself as the American “redeemer,” a man who would fix the country by acknowledging its past errors and charting a different course for the future.

Much of that had to do with changing what Obama saw as America’s bigoted view of Islam, before and after 9/11. Indeed, the Cairo speech was titled “A New Beginning.”

It has worked about as well as his “reset” with Russia.

In fact, it has made everything worse. Just as Obama’s persistent attempts to ban certain guns have led to record gun sales, his effort to put a smiley face on Islam has backfired. Too many Muslims in too many countries have responded to his retreat with more bloodthirsty violence.

From the spreading butchery of Islamic State to more frequent and lethal attacks at home, including San Bernardino and Orlando, Obama’s presumptions increasingly look ridiculous. While it is obvious that some American prejudice exists, the fundamental problem is that nearly all the world’s terrorists are Muslims — a fact acknowledged by the president of Egypt, among many others.

But the president of the United States can’t bring himself to make the same admission because he doesn’t want it to be true.

And because Obama is a partisan warrior, Americans are polarized and now fight each other almost as furiously as they fight the terrorists. The result, again, is the opposite of what he intended — a rising fear of Muslim terrorists, including among a new generation of Americans.

For all the complications that Obama is adding to the mix, it is fundamentally a simple situation: We are at war.

By his definition, Nazi and Japanese soldiers also could be called deranged fanatics filled with hate, but neither FDR nor Harry Truman tried to advance a nuanced explanation for their motivations. They saw the enemy as an evil force that had to be defeated.

That’s war. And this is war, and even though Obama wants America to forget, the terrorists have not forgotten us.

It’s penny foolish

Government money arrives in drips, and departs in rivers. State Comptroller Tom DiNapoli boasted the state’s pension fund, where he is sole trustee, had a “positive return.”

Technically true — it gained 0.19 percent. Or, as Politico put it, the fund “barely breaks even.”

Meanwhile, the city paid out $586 million in lawsuit settlements and verdicts last year, city Comptroller Scott Stringer said. That brings the two-year total to a whopping $1.14 billion.

In both cases, taxpayers get hosed.

Popcorn and booze

Common sense has been declared out of fashion in Albany. A Buffalo Democrat, Assemblyman Robin Schimminger, was blasted for opposing a bill to allow movie theaters to sell booze.

“He is still somewhat stuck in a previous era,” said fellow Dem Diane Savino of Staten Island, the bill’s Senate sponsor.

Yeah, he’s stuck all right — in exactly the right place. Who wants to pay $10 for a movie seat next to a chatty boozer?

Closing in on Hizzoner

The Wall Street Journal report that prosecutors are interviewing big donors to Mayor de Blasio’s political slush fund indicates that the probes are zeroing in on their targets. The paper says the interviews, which followed subpoenas for reams of documents, are focused on what, if anything, donors got for their dollars.

The development follows the filing of charges against the initial targets. Norman Seabrook, former head of the correction-officers union, and a hedge-fund operator were charged in an alleged kickback scheme that involved $20 million of pension money.

Numerous reports say the Seabrook probe led to one of de Blasio’s donors, businessman Jona Rechnitz. As part of the Seabrook charges, Rechnitz pleaded guilty to a charge of conspiracy and is cooperating with federal prosecutors in hopes of gaining leniency.

With Rechnitz singing, the decision on the mayor’s fate could come anytime. Given what is publicly known about favors he did for some of his big-bucks backers, it would count as a shock if he isn’t charged.