Submarines are armed with all sorts of deadly weapons, from torpedoes and mines to nuclear-tipped ballistic missiles.

But an AK-47?

Russian arms maker Rostec claims to have developed the first underwater drone to be armed with an assault rifle.

“It has undergone sea trials... Full-fledged trials will begin closer to the start of winter,” Rostec told Sputnik News. “It is a unique project since no one has so far fitted [an underwater drone] with small arms. Moreover, very few [countries] in the world have underwater automatic small arms.”

“The main purpose of the drone, which is designed and developed by Rostec subsidiaries, is to protect port facilities, bridges, naval bases and ships from enemy combat divers and underwater drones,” Sputnik News said. The drone was displayed at the Army 2018 defense trade show in Moscow this week.

Rostec did not specify what model of assault rifle is mounted on the drone. However, in the 1970s, Russia developed the APS underwater rifle, based on the AK-74 assault rifle but with a smoothbore rather than a rifled barrel. The APS fired darts, which had a more stable trajectory underwater than bullets.

Unmanned Underwater Vehicles, or UUVs, are becoming a regular part of naval warfare. The U.S. Navy is developing them for several missions, notably minesweeping, reconnaissance and surveillance, and anti-submarine detection. DARPA’s Mobile Offboard Clandestine Communications and Approach (MOCCA) program aims to pair a conventional Navy submarine with an underwater drone equipped with active sonar. Rather than the submarine disclosing its location by emitting sonar waves when it searches for enemy subs, it can deploy the UUV at a safe distance to do the searching—and light itself up as a target.

But armed robots are a different matter. The U.S. military vigorously emphasizes that when drones employ weapons, there is always a human in the loop to make the decision to pull the trigger.

The Rostec announcement of the rifle-armed UUV is short on details. How will the drone be controlled? By a surface ship, shore installation or a Russian combat diver in the water? Must humans give authorization to fire, or will the machine be capable of employing weapons autonomously?

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Nonetheless, the concept of an armed robotic sentinel is so logical as to be inevitable. One task at which robots excel is dull, routine work, such as patrolling a port to stop enemy divers from conducting reconnaissance or sabotaging ships. Already, machines are being used on land to patrol borders. Israel guards its border with Gaza with autonomous pickup trucks equipped with a 360-degree camera. South Korea has stationed SGR-A1 robots along the Demilitarized Zone with North Korea—the immobile robots are each armed with a machine gun that can fire automatically, though South Korea says that humans must give the order to fire.

Michael Peck is a contributing writer for the National Interest. He can be found on Twitter and Facebook.