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.