Here's What You Need to Remember:  But submarine modernization comes neither cheap nor fast, and the Kremlin is unlikely to unlikely to commit the massive resources required to replace every Soviet-era submarine in the Northern Fleet roster with a modernized equivalent.

From the Petr Velikiy battlecruiser to the Admiral Gorshkov frigate, Russia’s Northern Fleet is home to some of the newest, most advanced Russian surface ships. The same cannot be said of its aging submarine lineup, however. The Northern Fleet submarine force is largely comprised of 1980’s Soviet Detla IV and Sierra models, which are becoming increasingly harder and more expensive to maintain with incremental updates.

The Northern Fleet is now taking a major step to modernize its submarine force with a new hardware shipment slated for later this year. Admiral and Fleet Commander Nikolai Yevmenov informed Russian state news that, "In 2019, we are expecting the arrival of new logistics vessels and submarines."  Yevmenov added that the new submarines will be Knyaz Vladimir and Kazan, from the Borei and Yasen classes respectively.

Laid down in 2012, Knyaz Vladimir is the first entry in a newer line of 955A-- also known as Borei II-- submarines. The 955A generation brings several iterative improvements over its 955 predecessors: target acquisition upgrades, new onboard electronics, updated communication systems, and redesigned living quarters.

Knyaz Vladimir will join the very first Borei vessel, Yuri Dolgorukiy, in replacing the Delta IV line as the Northern Fleet’s staple strategic nuclear submarine. Generic performance improvements notwithstanding, the Borei line introduces a critical, sorely-needed update to Russia’s nuclear triad: the new Bulava missile system. Boasting a 550 kiloton warhead and an effective range of up to 10,000 kilometers, the Russian Navy seeks to make Bulava-equipped Borei vessels the cornerstone of their nuclear submarine-launched ballistic missile (SLBM) deterrent for decades to come.

On the tactical front, the introduction of Kazan marks a serious first step in the revitalization of the Northern Fleet’s decades-old attack submarine lineup. The second Yasen-class vessel, Kazan offers an expanded and markedly more deadly armament suite over its Akula and Oscar-class predecessors. Not only does the Yasen class support the standard submarine-launched variant of the Kalibr land attack cruise missile, but it apparently also accommodates the heavier, larger Kalibr-M missile with roughly double the range, at 4,500 versus 1,500 to 2,500 kilometers.

As the Arctic region becomes ever more militarized in the context of global Russia-NATO competition, it is hardly surprising that the Russian Navy is actively investing in the Northern Fleet. But submarine modernization comes neither cheap nor fast, and the Kremlin is unlikely to unlikely to commit the massive resources required to replace every Soviet-era submarine in the Northern Fleet roster with a modernized equivalent.

With two more Borei vessels commissioned over the next several years alone, the Delta IV line is on track to be completely phased out before 2040. But attack submarines pose a much more difficult value proposition, as a single Yasen vessel reportedly costs twice as much as its Borei counterpart.

So, where does the Northern Fleet go from here?

One potential route is consolidation; that is, saturating the Northern Fleet with modernized submarines at the expense of shrinking its total submarine roster. The other is iteration in the form of deep refits of existing submarines, as the Pacific Fleet has recently done with a modernized batch of old Kilo models.

Of course, the two are not mutually exclusive. It’s perfectly possible that Russia will opt for any number of hybrid development approaches; for instance, mass-producing new nuclear strategic submarines while extending the lifespan of existing attack submarines for as long as technically possible.