One of the depressing things about “homeland security” broadly defined is that it’s so elusive. If we choke off a threat at one point, our enemies will start probing for another weakness. Even if we do manage to build a fence on the border and get the visa process and airline security into reasonable shape, jihadists are going to look around for another place to get in and attack us. The logical place is the coastline.

Before the Mexican border became the preferred crossing point, much of the cocaine coming into America came through the Caribbean (in fact some have argued that the Coast Guard’s successful clampdown on stopping planes and boats into Florida caused the bulk of the smuggling industry to relocate into Mexico.) It’s also worth remembering that probably the only invasion of our mainland by enemy saboteurs during wartime happened on the coast.

Writing for the US Naval Institute’s magazine, Proceedings, (free registration required) retired Coast Guard Captain Robert C. Bennett has a look at what we’re doing and a few ideas about what ought to be done. Counter-mine sweeps, tracking small craft, and identifying likely targets like fuel depots are good ideas. Allowing foreign sailors off the ships for shore leave is less convincing, but he makes an interesting argument:

Unfortunately, the approach taken by MHS agencies appears to protect the ports from the merchant marine. Too many law enforcers tend to consider these merchant sailors as perpetrators or suspects. One particularly egregious manifestation of this policy restricts seamen from shore leave. While the restrictive security measures applied to merchant seamen has become acceptable, the application of similar restrictions to the many alien nationals among us—legal and illegal—including some who profess sympathy for the enemy, has not.

He also raises an interesting exit question: Physically, where does the war on terror switch from a war footing to a law-enforcement footing?

The problem may rest with our national policy of treating the war on terrorism as a law enforcement effort rather than a military campaign. In this strange war, we’ve come to consider our enemies as perpetrators, not non-uniformed combatants. Of course solid legal and bureaucratic reasons dictate this law enforcement approach, at least domestically. Given the natural flavor of law enforcement—respond to a reported crime, arrest the perpetrators, and bring them to justice—the MHS emphasis on first response is understandable. Nevertheless, waging a real war involves the application of many doctrines and behaviors that fall beyond the boundaries of conventional law enforcement. That’s why Soldiers are not police, and vice versa.

Law enforcement operations tend to be reactive while military operations, even when defensive, are proactive. In war, the goal is to annihilate the enemy or, at the least, neutralize whatever threats he might present. Thus, the importance of MHS proactive deterrence emerges because it serves to prevent the enemy from achieving a position from which he may successfully launch an attack on our maritime homeland.

See-Dub says check it out. It’s an overlooked but critical part of the big picture, especially since Iran (and by extension, Hezbollah) are gaining expertise in small-scale (but politically effective) maritime warfare.

ONE MORE THING: While you’re there, look at the pictures. Especially the one of the Iraqi tugboat with this caption:

BANG-IN-A-DRUM An Iraqi tug captured in 2003 carrying mines concealed in a “cargo” of 55-gallon oil drums could easily be the prototype for a makeshift minelayer to infiltrate U.S. waters.

UPDATE: Chertoff testified on the Hill today about DHS readiness, and “the threat of a USS Cole-type attack on U.S. ports — where a small boat packed with explosives detonates in a harbor — is one of his top concerns.”