How to defend your coast without sailors or guns

An engineer at the respected RAND Corporation has a suggestion for small countries that want to keep their enemies at bay but can't afford a proper navy: use loads of sea mines and drones. It seems obvious, but the advice could prevent America getting dragged into a world war.

Explosive ordnance disposal technicians simulate the destruction of a submerged mine.

(U.S. Navy photo by Petty Officer 1st Class Charles White)

Engineer Scott Savitz names a few countries in his RAND post, such as Bahrain, Taiwan, and the Republic of Georgia, two American allies and a potential future member of NATO. While all of them spend significant portions of their GDP on defense, they are all also potential targets of larger neighbors with much larger navies.

So, it's in the best interest of these countries (and the U.S.) if those countries can find a way to stave off potential invasions. RAND's suggestion is to spend money on mines and drones, which require much more money to defeat than they cost to create. This could cripple an invading fleet or deter it entirely.

While mines are a tried and true — but frowned upon — platform dating back centuries, modern naval tactics give them short shrift. Unmanned drones in water, air, and on land, however, are reaching maturity.

A Royal Norwegian Naval Explosive Ordnance Disposal Commando collects information during a mine-countermeasure dive during exercise Arctic Specialist 2018.

(U.S. Navy)

The idea is for the smaller nations to build up mine-laying fleets that go on regular training missions, laying fake mines in potentially vulnerable waters. This would create two major problems for invading nations: An enemy force capable of quickly saturating the water with mines as well as thousands of decoys that would hamper mine-clearing vessels.

And, mine clearance requires warships to sail relatively predictable patterns, allowing the defending nation to better predict where invading forces will have vulnerable ships.

The drones, meanwhile, could be used for laying mines, directly attacking enemy ships, conducting electronic surveillance, or even slipping into enemy ports to attack them in their "safe spaces" — a sort of Doolittle Raid for the robot age. They could even be used to target troop transports.

While the Russian, Iranian, and Chinese Navies are much larger than their Georgian, Bahrain, and Taiwanese counterparts, they don't have much sea-lift capability, meaning that the loss of even a couple of troop ships could doom a potential invasion.

All of these factors could combine to convince invading forces to keep their ships at home, or at least slow the attacking force, meaning that reinforcements from the U.S. or other allied forces could arrive before an amphibious landing is achieved.

It's easier to contest a landing than it is to throwback an already-fortified foothold.

A underwater drone used to measure salinity, temperature, and depth information is recovered by the U.S. Navy during normal operations.

(U.S. Navy)

For Bahrain and Taiwan, both island nations, ensuring that an enemy can't land on their coast nearly protects them from invasion. As long as their air forces and air defenses remain robust, they're safe.

The Republic of Georgia, on the other hand, has already suffered a four-day land invasion from Russia. While securing their coastline from naval attack would make the country more secure, it would still need to fortify its land borders to prevent further incursion.

A Navy drone, the Fire Scout, lazes a target for the MH-60 Sea Hawk helicopter that accompanies it.

(U.S. Navy photo by Mass Communication Specialist Third Class Trenton J. Kotlarz)

For America, allies that are more secure need less assistance and are less likely to collapse during invasion without large numbers of American reinforcements.

But, of course, mines remain a controversial defense measure. They're hard and expensive to clear, even after the war is over. And while sea mines are less likely to hurt playing children or families than leftover landmines, they can still pose a hazard to peacetime shipping operations, especially for the country that had to lay them in the first place.