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A nation at war needs to secure its borders.

It is simply astonishing that a statement like that—a matter of simple common sense and basic national sovereignty—is politically controversial.

It is simply astonishing that we’re left debating—like we did last week—whether the arrest of four self-proclaimed Middle East terrorists represents a warning that our borders need to be more secure.

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Yes, we know that the Obama administration and its liberal allies in Congress remain ideologically and politically committed to an open border. They see unrestrained immigration as a foundational piece of their bid for long-term Democratic dominance.

But are they so committed to this partisan vision that the clear and present danger of terrorist infiltration from an open border is insufficient to cause concern?

And it’s not just the border with Mexico that’s porous. We’re not even properly monitoring young American men who return home after fighting with ISIS – the Islamic State.

A 22-year-old American, Moner Mohammad Abusalha, flew home from Syria and landed in Newark, New Jersey, where U.S. officials checked out his story of visiting relatives in the Middle East by . . . calling his mom.

When she vouched for him, he left the airport and traveled into the American heartland, completely unmonitored.

He flew back to Syria and blew himself up -- ISIS’s first American suicide bomber. But before he left, he recorded a video where he declared: “You think you are safe where you are in America . . . you are not safe.”

Obviously not.

Given this story, can Americans have any confidence that we’re actually monitoring and controlling the 40 ISIS terrorists that Democratic congressman Tim Bishop says are already in this country, under FBI surveillance?

The story of America's border security is a story of incompetence, wishful thinking, and hard-Left ideology.

It’s incompetent to allow a mother’s word to validate her terrorist son’s intentions.

It’s wishful thinking to believe that our government—despite establishing FBI and CIA task forces—can adequately track all of the jihadists traveling to and from the strategic heart of the Middle East. After all, we’ve proven we can’t track everyone that flies into Newark. How can we be sure we’re tracking jihadists who fly into Mexico City?

It’s hard-left ideology that places so much importance on an open border that it will not yield unless or until there is a major attack or other tragedy.

No one can reasonably dispute that our southern border is extraordinarily porous. After all, if it can be easily crossed by tens of thousands of unaccompanied minors, how much easier is it for trained terrorists to cross unseen?

But the hard left refuses to listen to reason, arguing that the issue isn’t serious unless there is definitive proof that the border has already been penetrated.

But, as with most terror attacks, we won’t know that our vulnerabilities have been exploited until after the bombs detonate, until after Americans die.

Here’s a common sense proposal: Let’s protect Americans and then work out how many immigrants we want in the country. One is not anti-immigrant when one declares that a sovereign nation should know—and control—who comes into its country.

Let’s let our people decide—through the democratic process—how much immigration we want and need, but while we’re making that decision, let’s not leave our national security to chance.

As I point out in a new book, "Rise of ISIS: A Threat We Can’t Ignore," we’re rolling the dice every day, hoping and praying that terrorists cannot or will not exploit our known vulnerabilities—that they won’t come to this nation despite their promises to do so.

We don’t always know when terrorists will strike. The morning of September 11, most Americans had confidence in airport security. The morning before the Boston Marathon bombing, tens of thousands of spectators and runners were completely unaware of the horror that waited.

That’s the way terrorists work -- through shock and surprise.

But if terrorists infiltrate our borders and shatter the calm of a future American morning, we may be surprised, but we should not be shocked.

After all, our political leaders will have chosen to leave our national door wide open.