By Aaron Kliegman Too often we as a society frame immigration as a social, cultural, or economic issue. It’s understandable: We normally discuss immigration in relation to the law, national identity, or jobs. But fundamentally, immigration is an issue of national security — just as choosing who you let into your home is an issue of personal and familial security. We were reminded of this basic yet crucial fact earlier this week, when federal authorities said they caught two suspected terrorists crossing the southern border. Specifically, US Customs and Border Protection (CBP) revealed Monday that, in recent months, the agency arrested two Yemeni men for illegally entering the US from Mexico. Agents busted the men, ages 33 and 26, near the Calexico Port of Entry in California in separate incidents on Jan. 29 and March 30. Here’s where national security really comes into play: Authorities then discovered by checking their records that both men were on not only a “no-fly” list but also a government watchlist for people suspected of terrorism. One reportedly had a cellphone SIM card hidden in his shoe. According to the FBI, the watchlist includes people who are “known to be or reasonably suspected of being involved in terrorist activities.” Two of them were just trying to enter our national home illegally. And they’re not the only ones. Yikes. CBP’s announcement came amid a surge in the number of migrants seeking entry in the US. Which begs the question: How many seek to do us harm, and how many have crossed the border successfully? We just don’t know. There’s not enough publicly available data. True, few people who entered the US illegally have been convicted of planning a terrorist attack on American soil, and even fewer have been injured or killed by terrorist attacks. But that doesn’t refute the commonsensical point that a relatively open and vulnerable southern border is an appealing option to hurt “the Great Satan” for those who wish us harm. Indeed, our enemies would be morons not to exploit this vulnerability — America’s literal underbelly. Plus, when we look at illegal immigration as a matter of national security, terrorism isn’t the only threat. Of perhaps greater concern is espionage — the prospect of adversarial countries such as Iran sending agents to spy rather than attack. Just in February, US Border Patrol caught 11 Iranians crossing the southern border from Mexico into Arizona. The Iranians may be ordinary migrants with nothing to hide. But it wouldn’t be surprising if one or more were on a more nefarious mission than just entering the US illegally — which, by the way, is illegal in and of itself. In fact, Iran has deeply entrenched itself in Latin America through its chief proxy, Lebanese Hezbollah. Both Iran and Hezbollah are deeply involved in drug trafficking and a host of other criminal activities across the region. Add the fact that Iran and Hezbollah have plotted to attack Americans and others on American soil in the past, and it becomes clear that this threat cannot be ignored. Critics will say all this is paranoid, even conspiratorial thinking. It’s not a coincidence that these are the same voices fighting serious efforts to secure our borders more effectively. Indeed, they were probably happy to learn that, one day after announcing the apprehension of the two Yemeni men, CBP took down its press release. Presumably, if federal authorities stop more suspected terrorists trying to cross the border, we won’t hear about it. What a relief: Now we don’t need to worry about the problem. We can just close our eyes and ignore it — and, like magic, the threat will surely go away. Because there’s absolutely no way imaginable that terrorists or foreign governments would ever exploit our southern border to attack or spy on us. After all, the more open our borders, the more benign we are, and the more the rest of the world likes us. That’s how it works, right?