The Russian submarine Dmitry Donskoy, the world's largest in active service, arrives at Kronstadt Navy base, outside Saint Petersburg, on July 26. (OLGA MALTSEVA/AFP/Getty Images)

Regarding the Dec. 23 front-page article "NATO on edge as Russian subs near undersea cables":

The threat is in the future: The yard at Severodvinsk, Russia, can produce more submarines per year than can both U.S. submarine builders combined (nonnuclear submarines also are being built at St. Petersburg).

While the U.S. Navy initiates a new submarine design every decade or two, the Russian submarine design bureaus Malachite and Rubin are continuously developing new undersea craft.

There also is the threat of another "Alfa surprise": The nuclear submarine Alfa that went to sea in 1971 was a shock to the West, being faster than any U.S. submarine, more automated, with more safety features and constructed of non-magnetic titanium — all features that took Western intelligence by surprise. (The Alfa's advanced, liquid-metal reactor plant did have major problems and was not repeated in later submarine classes.) Subsequent Soviet-Russian submarines could dive significantly deeper than their U.S. counterparts, carried more weapons and had other advanced features.

Undersea warfare most likely will be a key component of future crises and conflicts.  Considerably more attention must be paid to this area of U.S. defense.

Norman Polmar, Alexandria

The writer is co-author of "Submarines of the Russian and Soviet Navies"
and "Cold War Submarines."