The Russian submarine that just showed up off of Cuba is one of a new class of subs that has worried the US and NATO for years

• Russian naval ships arrived in Cuba on Wednesday ahead of military exercises in the Caribbean.
• One of the vessels, the submarine Kazan, is one of a new class that has worried the US and NATO.
• The Yasen-class subs are quiet, difficult to track, and heavily armed for attacks against land- and sea-based targets.

One of Russia's most concerning new submarines has pulled up off the coast of Cuba ahead of planned military exercises in the area.

The Kazan, a nuclear-powered cruise missile submarine, is one of a relatively new class of subs that has worried the US and Western militaries for years due to its stealth and strike capabilities .

Three Russian ships, as well as the Kazan, arrived in Cuba on Wednesday for a five-day official visit before a large, simultaneous air and maritime exercise in the Caribbean. The deployment includes the Admiral Gorshkov frigate, which is armed with Zircon hypersonic missiles, another challenge for Western militaries.

While US officials have said they're monitoring the vessels and don't anticipate any imminent danger in the region, the Kazan's arrival is notable. US and NATO officials have long expressed anxiety over the capabilities of the Kazan and other subs like it.

Russia's Yasen-class submarines, like the Kazan, are formidable threats within Russia's navy, which has long boasted a rather capable submarine fleet. The Russians began work on the class during the Cold War , and the first sub in the class, the Severodvinsk, was commissioned late in 2013.

Around the time the Severodvinsk came about, Naval Sea Systems Command's program executive officer for submarines said at a naval symposium that going forward, the US would "be facing tough potential opponents," adding that "one only has to look at the Severodvinsk."

After the Severodvinsk was commissioned into the Russian navy, later submarines featured updated designs , designated as part of the Yasen-M class. The Kazan was the second sub of the class but the first of the new upgraded subs. It is noticeably smaller and features a quieter nuclear reactor.

The subs' newer, more advanced features make them quiet, difficult to track, heavily armed, and capable of attacks against land- and sea-based targets with little to no notice. These warships can carry Oniks and Kalibr cruise missiles and, at a later date, the new Zircon missiles.

The shift in capability with the emergence of the Yasen-M class submarines suggested a change in use. Per a 2021 Royal United Services Institute analysis , the Kazan's "capacity to launch a range of anti-ship and land attack missiles" suggests that "long-range strike missions appear to be superseding sea lines of communication (SLOC) interdiction as a primary task."

In 2021, US Air Force Gen. Glen VanHerck, head of US Northern Command and North American Aerospace Defense Command, said that the subs "are designed to deploy undetected within cruise-missile range of our coastlines to threaten critical infrastructure during an escalating crisis."

VanHerck, along with other US officials, have said the Yasen-class subs are " on par with ours " and repeatedly warned about the increasing presence of these vessels off of the US coast.

Russia plans to build at least nine Yasen submarines in total, but there are indications that more could be on the way in the future .

Russia's deployment in Cuba serves multiple purposes. It comes before Caribbean air and maritime exercises, the first Russia's held in the area since 2019. It serves to strengthen Russia-Cuba ties. And it demonstrates a show of force to the US amid the war in Ukraine.

Tensions are particularly high after the US hesitantly agreed to allow Ukraine to use its long-range weapons to strike targets in Russian territory .

US officials have said that movement of these vessels into the area is not a direct response to these developments or an escalation, noting that Cuba has hosted Russian ships every year from 2013 to 2020, and the Russian exercises are routine.

The vessels in this group, however, are notably among Russia's more advanced or carrying newer weapons. In the past, NATO officials have flagged the Yasen-class submarines, for instance, as "one of the big strategic challenges" the alliance faces.