One of Russia’s oldest and stealthiest submarines is set to reenter service soon, after repairs are completed, with crews expecting the ship to be redeployed by the end of May.

The Russian Navy is working to complete repairs to the Alrosa this week, sending it to the Bay of Kilen for final tests to ensure there are no faults with the design before it reenters the Black Sea fleet, according to Russian officials. Crew members are also expected to complete tests before being given the green light to man the Soviet-era submarine.

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"The Plant’s workforce has fulfilled a large amount of work, as a result of which the Alrosa has been not only repaired but has also acquired new combat and technical capabilities,” the Black Sea Fleet’s 13th Ship Repair Plant said in a statement. “They put the submarine on a par with six submarines that have become operational in the Black Sea Fleet in recent years.”

BSF diesel-electric submarine Alrosa
Russian Navy's best diesel submarine Alrosa is moored in the port of Sevastopol on March 19, 2013. (ZUMA Press/Newscom)


The submarine was built shortly before the Soviet Union dissolved in 1991 as part of the experimental Project 877, a training ship class that began in the 1970s. After the Soviet Union collapsed, the Alrosa became Russia’s only combat-fit submarine to be used in the Black Sea.

The ship was designed to move via waterjet engines rather than by propeller propulsion to ensure stealth as it traveled underwater, earning the nickname “black holes” worldwide.

BSF diesel-electric submarine Alrosa
Inside the Russian Navy's submarine Alrosa on March 19, 2013. (ZUMA Press/Newscom)


The latest development comes as the Russian navy has taken hits over the last several weeks, with at least four or five significant vessels being destroyed in March and April, including the sinking of the Moskva, which was one of the biggest blows to the Russian military since its invasion in late February.

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The Moskva is the largest Russian warship to be sunk in combat since World War II. After the losses of the Moskva and the Saratov, Russia had approximately 20 ships in the Black Sea, a British Defense Ministry's intelligence update said last month.

Russia continues to have capabilities to hit targets on Ukraine's mainland from the sea, but replacing its sunken ships is not possible with a key Turkish-controlled strait closed to most warship traffic, the bulletin added.