Trained to carry out military tasks, they were seized during the annexation of Crimea. Kiev wants them back – but Russia has plans for the cetaceans

It wasn't just the miles of gorgeous coastline, the plush dacha compounds of the Soviet elite and the naval bases of the Black Sea Fleet that Russia acquired when it annexed Crimea this year; it was also Ukraine's combat dolphins, part of a secret programme that trains sea mammals to carry out military tasks.

Now, however, Ukraine is demanding the return of the dolphins, who unlike the naval officers serving on the peninsula, were not given the choice of "defecting" to Russia or travelling to mainland Ukraine to continue serving Kiev.

The dolphins are still being held at an aquarium near Sevastopol, but Ukrainian authorities in a town across the isthmus from Crimea say they have a facility where the cetaceans could spend the rest of the summer before a new military home is found for them.

The Ukrainian military dolphin programme was born out of a Soviet-era scheme that, like much of the Soviet army, fell into neglect in the 1990s. There were reports in 2000 that the dolphins had been sold to Iran.

The programme was resurrected in 2012 by the Ukrainian navy, and the Crimean military dolphin centre is thought to be one of just two in the world, with the other in San Diego serving the US navy, where around 75 dolphins are trained, along with sea lions.

However, Ukraine's military infrastructure in Crimea was destroyed by Russia during the annexation of the territory. Russian troops surrounded military bases and demanded that the Ukrainians surrender or defect, a process that took several weeks but passed off without major bloodshed. Some military equipment was seized, while some was dispatched to the rest of Ukraine, which is what Kiev would now like to see happen to the dolphins.

The Russians, however, have big plans for their newest naval recruits. A source told Russian agency RIA Novosti back in March that with Crimea part of Russia, serious investment in dolphin preparation was now on the cards.

"Engineers are developing new aquarium technologies for new programmes to more efficiently use dolphins under water," said the source, telling the agency that dolphins and seals would search for sunken military equipment and detect enemy divers.

"Our specialists developed new devices that convert dolphins' underwater sonar detection of targets into a signal to the operator's monitor. The Ukrainian navy lacked funds for such know-how, and some projects had to be mothballed."