WASHINGTON — The new conventional wisdom on 9/11: We have created a decade of fear. We overreacted to 9/11 — al-Qaida turned out to be a paper tiger; there never was a second attack — thereby bankrupting the country, destroying our morale and sending us into national decline.

The secretary of defense says that al-Qaida is on the verge of strategic defeat. True. But why? Al-Qaida did not spontaneously combust. Yet, in a decade Osama bin Laden went from the emir of radical Islam, jihadi hero after whom babies were named all over the Muslim world — to pathetic old recluse, almost incommunicado, watching shades of himself on a cheap TV in a bare room.

What turned the strong horse into the weak horse? Precisely the massive and unrelenting American war on terror, a systematic worldwide campaign carried out with increasing sophistication, efficiency and lethality — now so cheaply denigrated as an “overreaction.”

First came the Afghan campaign, once so universally supported that Democrats for years complained that President Bush was not investing enough blood and treasure there. Now, it is reduced to a talking point as one of the “two wars” that bankrupted us. Yet Afghanistan was utterly indispensable in defeating the jihadis then and now. We think of Pakistan as the terrorist sanctuary. We fail to see that Afghanistan is our sanctuary, the base from which we have freedom of action to strike Jihad Central in Pakistan and the border regions.

Iraq, too, was decisive, though not in the way we intended. We no more chose it to be the central campaign in the crushing of al-Qaida than Eisenhower chose the Battle of the Bulge as the locus for the final destruction of the German war machine.

Al-Qaida, uninvited, came out to fight us in Iraq, and it was not just defeated but humiliated. The local population — Arab, Muslim, Sunni, under the supposed heel of the invader — joined the infidel and rose up against the jihadi in its midst. It was a singular defeat from which al-Qaeda never recovered.

The other great achievement of the decade was the defensive anti-terror apparatus hastily constructed from scratch after 9/11 by President Bush, and then continued by President Obama. Continued why? Because it worked. It kept us safe — the warrantless wiretaps, the Patriot Act, extraordinary rendition, preventive detention and, yes, Guantanamo.

Perhaps, says the new conventional wisdom, but these exertions have bankrupted the country and led to our current mood of despair and decline.

Rubbish. The total costs of “the two wars” is $1.3 trillion. That’s less than 1/11th of the national debt, less than one year of Obama deficit spending. During the golden Eisenhower 1950s of robust economic growth averaging 5 percent annually, defense spending was 11 percent of GDP and 60 percent of the federal budget. Today, defense spending is 5 percent of GDP and 20 percent of the budget. So much for imperial overstretch.

Yes, we are approaching bankruptcy. But this has as much to do with the war on terror as do sunspots. Looming insolvency comes not from our shrinking defense budget but from the explosion of entitlements. They devour nearly half the federal budget.

As for the Great Recession and financial collapse, you can attribute it to misguided federal policy pushing homeownership through risky subprime lending. To Fannie and Freddie. To greedy bankers, unscrupulous lenders, naive (and greedy) homebuyers. To computer-enabled derivatives so complicated and interwoven as to elude control. But to the war on terror? Nonsense.

9/11 was our Pearl Harbor. This time, however, the enemy had no home address. No Tokyo. Which is why today’s war could not be wrapped up in a mere four years. It was unconventional war by an unconventional enemy embedded within a worldwide religious community. Yet in a decade, we largely disarmed and defeated it, and developed — albeit through trial, error and tragic loss — the means to continue to pursue its remnants at rapidly decreasing cost. That is a historic achievement. Our current difficulties and gloom are almost entirely economic in origin, the bitter fruit of misguided fiscal, regulatory and monetary policies that had nothing to do with 9/11. America’s current demoralization is not a result of the war on terror. On the contrary. The denigration of the war on terror is the result of our current demoralization, of retroactively reading today’s malaise into the real — and successful — history of our 9/11 response.

Charles Krauthammer is a Washington Post columnist. His email address is letters@charleskrauthammer.com.