by DAVID AXE

A photo depicting an American nuclear-powered submarine poking its periscope above the waves—within shooting distance of a British aircraft carrier during a war game—is a useful reminder of one of the most important truths of naval warfare.

For every sailor who’s not in a submarine, submarines are real scary.

Stealthy and heavily-armed, subs are by far the most powerful naval vessels in the world for full-scale warfare—and arguably the best way to sink those more obvious icons of naval power, aircraft carriers.

The public may not fully appreciate submarines’ lopsided combat advantage, but the world’s leading navies sure do. Today Chinese, Russian and American submarines, among others, are busy sneaking up on, tracking and practicing sinking rival fleets’ flattops.

The provocative photo, above, depicts the masts of the U.S. Navy attack submarine USS Dallas near the carrier HMS Illustrious during a naval exercise in the Gulf of Oman on Oct. 3, 2013. Six warships including Dallas and Illustrious conducted an anti-submarine-warfare exercise that saw Dallas stalking Illustrious while British and American surface warships and helicopters attempted to locate and “sink” the undersea vessel.

Neither navy has published the results of the exercise, so it’s not clear whether Dallas got close enough in the course of the war game to simulate firing Mark-48 torpedoes at the flattop, which at 22,000 tons displacement is one of the largest ships in Royal Navy service.

But there are good reasons to assume the 7,000-ton Dallas did succeed in pretend-sinking Illustrious. In 2007 HMCS Corner Brook, a diesel-electric submarine of the Canadian navy, sneaked up on Illustrious during an exercise in the Atlantic.