After 9/11, the prevailing view was that “nothing would ever be the same.” The sight of bodies plunging 100 stories from the flaming towers of the World Trade Center seared into our psyches the reality that America has cruel and wanton enemies. The USA Patriot Act, which sought to repair some of the intelligence lapses that permitted the 9/11 attacks to go undiscovered, passed the House by a vote of 357 to 66 and the Senate by 98 to 1.

Twelve years is a long time, though, and the best you can say about “things will never be the same” is that it’s a truism. The ordinary human tendency to relax one’s watchfulness creeps back surprisingly quickly — especially when the president of the United States implies that we can unilaterally declare a war “ended” because we’re tired of vigilance and we want to spend money on Obamacare, universal preschool and food stamps.

The Obama administration is flailing on the subject of national security, declaring the war over in one breath and thundering against Syria’s use of chemical weapons in the next. After 12 years of excoriating George W. Bush for attempting to deal with a tyrant in control of WMDs, Barack Obama, though calling himself “war-weary,” nonetheless sounded exactly like his predecessor in his frustration with the so-called “international community.”

“My preference obviously would have been that the international community already acted forcefully,” he lamented on Friday. “But what we have seen … is an incapacity at this point for the Security Council to move forward.”

What caused that “incapacity”? Russia’s willingness to veto any resolution that would impose costs on Syria. Thus does the law professor encounter the real world, in which promising “resets” and “flexibility” to “Vladimir” leads not to international cooperation against evil but to the opposite.

If the president were thinking strategically, and not just about avoiding personal humiliation because he improvidently painted himself into a corner with warnings about “red lines,” he wouldn’t be wasting energy on Syria, which is the client of another power. As Michael Ledeen of the Foundation for the Defense of Democracies has tirelessly pointed out, Iran is the chief fount of terror in the world. Ledeen is feeling deja vu, watching another president focus on the wrong country regarding WMDs.

The president’s claim that Syria’s use of chemical weapons “threatens our national security interests” is clearly absurd. The danger Syria poses is simply to Obama’s diminishing credibility. Chemical weapons are ghastly, but our revulsion at their use doesn’t amount to facing a threat. Besides, the president’s proposed military wrist-slap will probably have no effect — except to further erode the world’s respect for American power.

Iran, by contrast, is a menace. Iran hasn’t used chemical weapons on its own people (it tortures and kills in other ways), yet as the chief supporter and weapons supplier to Hezbollah, Hamas and other terror groups, and as a sometime partner to al-Qaida, it does threaten us. Since taking our diplomats hostage in 1979, the Islamic Republic has kept up attacks on the U.S. directly (in Iraq), expanded Hezbollah into South America, allied with American foes like Venezuela and attacked us through terror proxies (as in the 1983 bombing of the Marine barracks in Lebanon).

Obama is relying on the same “international community” that has proved so useless on Syria to deter Iran from developing nuclear weapons. Yet he doesn’t seem worried, which is worrying.

If Bashar Assad gases the Syrian people with Sarin, it offends our sensibilities. But if the mullahs of Iran achieve their goal of getting nuclear weapons, it is conceivable that nuclear terror could threaten the American people.

Would Iran be deterred as the Soviets and Chinese were by the threat of retaliation? Maybe, but would you trust the lives of your children to that guess? The point about arming terrorists — as the Iranians have been doing for 35 years — is that it provides deniability. If a dirty bomb were detonated in Chicago, would we retaliate against Tehran on the suspicion that the mullahs provided the uranium? We cannot even agree that our intelligence proves Assad used poison gas.

Every foreign policy action should be judged, not by whether it advances a naive fantasy of a world community punishing a miscreant, but by whether it advances American security. That means thwarting Iran by all means necessary.