Russia and the United States have both long trained marine mammals to do their martial bidding. Two pens of Russian-trained military dolphins have been spotted near a Sevastopol harbor and are likely being used to defend the port.
The dolphins at the mouth of the Crimea port are likely used to deter underwater sabotage attempts. It is unclear if any are also used as explosive devices. Russia kept its dolphin training base in Crimea after its annexation in 2014. The Moscow Times reported at the time that Russia was training the dolphins to plant explosives on ships.
The U.S. has used highly trained dolphins and sea lions for similar activities since the 1960s, according to the Washington Post. North Korea and Israel also reportedly have military mammal programs for defensive purposes.