Last month, Russia's defence ministry announced that it was looking to recruit five bottlenose dolphins with "perfect teeth and no physical impairments" to join the ranks of its military. Officials didn't elaborate on what exactly the dolphins would be doing once "drafted", but if the country's past history with military dolphins is any indication, they won’t be performing tricks for tourists.

During the Cold War, both the Soviet and US navies employed the services of marine mammals, with dolphins being used for everything from search and rescue, to mine detection and espionage. Possibly even assassination.

But if you’re unfamiliar with the weird world of military dolphins, here are a few trivia tidbits to get you started.

U.S. Navy dolphins fought in Vietnam

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A US Navy Marine Mammal Program dolphin, wearing a locating pinger, performs mine clearance work in the Persian Gulf during the Iraq War. Image: US Navy/Public Domain 

The United States Navy has been training dolphins for military purposes since the launch of its Marine Mammal Research Program in 1961. The animals been deployed in multiple conflict zones (including the Persian Gulf and even the 1996 Republican National Convention in San Diego), and were given a vital role during the Vietnam War.

In the late 1960s, US vessels in Cam Ranh Bay, a military port in South Vietnam, were being rigged with explosives by North Vietnamese frogmen. Unable to easily detect the combat swimmers, the Navy opted to bring in its most highly skilled underwater tracking team: bottlenose dolphins. The animals had been trained to scan the bay with their echolocation to zero in on the enemy. Their mission? To stab the frogmen in the buttocks with a steel hook attached to a balloon, which then inflated and pulled the frogmen to the surface, where they could be recovered by US forces. The technique was so effective that North Vietnam abandoned its sabotage activity in Cam Ranh Bay altogether. 

The Soviets might have trained dolphins to kill people

"Dolphin assassins" belong in the realm of sci-fi, right? Actually, there is good reason to believe that the Soviets probably did train their cetacean recruits to attack enemy divers. While the U.S. Navy strongly denies that it ever trained its dolphins to harm humans (other than lightly stabbing them with steel hooks), numerous sources suggest that Soviet military dolphins had been trained to place mines on enemy ships, as well as disable, capture, or kill enemy divers.

After the collapse of the Soviet Union, some of these “killer” dolphins were purportedly sold to Iran, whereas others remained at the seaside port of Sevastopol in Crimea, where they flipped their military careers for a new life of swimming with tourists. When Russia annexed Crimea in 2014, it vowed to rekindle the former military dolphin programme at Sevastopol, which might well be the reason it's now looking to buy new dolphins to fill its ranks.   

Military dolphins keep escaping. OR do they?

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Did someone say knives, firearms and toxic dart guns? 

After Hurricane Katrina devastated the Gulf of Mexico in 2005, the media reported that 36 U.S. Navy dolphins armed with “toxic dart guns” had been washed out to sea, and were roaming the Gulf looking for human victims. A similarly terrifying report emerged in 2013, warning that a handful of former Soviet military dolphins (with firearms and knives strapped to their heads) had gone missing in the Black Sea after escaping during a training exercise. Like so many other “escaped killer dolphin” news stories, both these reports turned out to be bogus. The Soviet dolphins never escaped. And even though U.S. Navy dolphins have occasionally gone AWOL, the dolphins in the Gulf were actually from Mississippi's Marine Life Oceanarium.

Palestine once captured an Israeli dolphin spy (Supposedly)

The long-running conflict in the Middle East has spawned a long list of implausible news reports involving animals being used in espionage and military operations. There was the story of a Mossad-trained killer shark sent by the Israelis to an Egyptian beachside resort to cripple the tourism industry. And who could forget the Israeli vulture sent to spy on Saudi Arabia, or the supernatural rats trained to destroy Arab cats? But nothing beats the story of the Israeli-trained dolphin spy purportedly caught by Hamas forces off the Gaza coast in 2015. The murderous dolphin was equipped with “espionage equipment, including video-recording cameras” as well as “small arrows and bullets to enable it to target humans.” In a rather unexpected and exciting twist to this story, it was later reported that the killer dolphin was in fact a robot. Suffice it to say, none of these reports have been confirmed.