Unlike the U.S. Navy, both Russia and China continue to operate non-nuclear attack submarines in addition to nuclear ones. These can still be extremely potent. They are cheaper and have some advantages compared to nuclear boats, especially inshore. And they can be exported to other countries. Now Russia and China may pool their knowledge to develop the next generation of non-nuclear sub. But exactly what it will be, or why, is still a mystery.
Forbes: China and Russia in mysterious new submarine project
Russian submarines area picture at the Russian naval base in the Syrian Mediterranean port of Tartus on Sept. 26, 2019.
