The Project 636 Varshavyanka is a class of diesel-electric submarines developed by Russia for the Russian Navy. These submarines are designed for anti-submarine warfare, anti-surface warfare, and intelligence gathering. They are known for their stealth capabilities, allowing them to operate undetected in various maritime environments. The Varshavyanka class is an improved version of the earlier Kilo-class submarines, featuring advanced sonar systems and weaponry. They can carry a range of torpedoes and cruise missiles, enhancing their combat effectiveness. The submarines are primarily used in the Black Sea, Mediterranean Sea, and Pacific Ocean.