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As Oval Office speeches go, it wasn’t much. Even so, we will look back on President Obama’s speech announcing the end of the Iraq War as one of great significance. Not because of what he said, but because of what he didn't say. He talked about Iraq, Afghanistan and the American military. But he didn't talk about the elephant in the room – IRAN.

And in the end, how Obama deals with Iran will be the defining national security issue of his presidency. Iran will be Obama's War, whether he chooses to fight it or not.

Recently his NSC point man on nuclear proliferation, Gary Samore, said Iran was a year away from having a nuclear weapon; in other words, whether Iran becomes a nuclear weapons state will happen on Obama's watch. It's a problem he can't kick down the road, blame on his predecessor, or throw up his hands saying well...he tried.

If Obama does nothing to stop Iran from going nuclear, it will set off a nuclear arms race throughout the Middle East, as one unstable country after another pursues nuclear weapons of their own. Once the region is "nuked up," the likelihood that one is used, accidentally, intentionally or inadvertently, goes up exponentially.

If Obama launches a preemptive attack against Iranian nuclear sites, he risks setting off a larger regional war, as Iran retaliates by potentially unleashing its terrorist proxies, awakening terrorist sleeper cells, or mining the Strait of Hormuz, cutting off some 40% of the world's oil exports. If Obama stands by while Israel attacks Iran, he is complicit since Israel would have to overfly U.S. air defenses in Iraq, and possibly drain into a third Middle East war. There are no good options with Iran, but his speech may have made things worse.

Think about it from Iran's perspective. Iran has supplied and trained our enemies in Iraq and Afghanistan; they're interfering behind the scenes in Iraq's elections and attempts to form a government. They're the world's major state sponsor of terrorism, and that they bankroll Hamas and Hezbollah. Their Hamas clients just murdered four innocent Israeli civilians, including a pregnant woman, in an supposedly safe area. They're beavering away on a nuclear weapons program, enriching uranium, testing long range missiles, firing up a nuclear energy plant no one believes has a peaceful intent.

What did Iran's leaders hear from Obama's speech? They heard President Obama say we were on our way out of Iraq, and we had a deadline for getting out of Afghanistan. They heard him say we had "wasted" a trillion dollars we could otherwise have spent stimulating the economy and rebuilding America's infrastructure. They heard a president who has made outreach to the Muslim world a top priority, and who received a Nobel Peace Prize just for not being George Bush, who didn't condemn them or even slap them on the wrist.

By not calling Iran out, even as he proclaims our troops are leaving the region, President Obama may have inadvertently given them a green light.

Kathleen Troia "K.T." McFarland is a Fox News National Security Analyst and host of FoxNews.com's DefCon 3. She is a Distinguished Adviser to the Foundation for the Defense of Democracies and served in national security posts in the Nixon, Ford and Reagan administrations. She wrote Secretary of Defense Weinberger’s November 1984 "Principles of War Speech" which laid out the Weinberger Doctrine. Be sure to watch "K.T." every Monday at 10 a.m. ET on FoxNews.com's "DefCon3" already one of the Web's most watched national security programs.

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