In an exclusive interview, the commander of U.S. Naval Forces in Europe told CNN that the buildup reflects an alarming strategic world view.
"NATO is viewed as an existential threat to Russia, and in the post-Cold War period, the expansion of NATO eastward closer to Russia and our military capability they view as a very visceral threat to Russia," Adm. Mark Ferguson said.
Ferguson spoke from his base in Naples, Italy, home to U.S. Naval forces in Europe and the Navy's 6th Fleet.
Adding to U.S. apprehension, Russia is deploying new submarines that are harder for U.S. naval forces to track and detect following years and billions of dollars in investment.
They are quieter, better armed and have a greater range of operation.
"The submarines that we're seeing are much more stealthy," Ferguson said. "We're seeing (the Russians) have more advanced weapons systems, missile systems that can attack land at long ranges, and we also see their operating proficiency is getting better as they range farther from home waters."
The U.S. currently has 53 submarines in its inventory, but because of decommissioning and budget decisions, Ferguson said that figure will drop to 41 by the late 2020s.
"We cannot maintain 100% awareness of Russian sub activity today," retired Adm. James Stavridis, a former NATO supreme allied commander, told CNN. "Our attack subs are better, but not by much. Russian subs pose an existential threat to U.S. carrier groups."
Russia plans on adding an additional six Kilo-class subs to the Black Sea Fleet, along with 14 to 18 diesel-electric submarines similar to Lada-class subs over the next 15 years.
Russia plans to replace its Delta III- and Delta IV-class submarines with Borei II subs in the coming years. The Oscar II class will be replaced with the new Yasen class after 2020.
- 13 Ballistic missile submarines (SSBN)
- 7 Cruise missile submarines (SSGN)
- 18 Attack submarines (SSN)
- 21 Attack submarines (SSK)
- 2 Special-purpose submarine