A US attack submarine and one of Russia's most formidable subs are in Cuba at the same time

• A US Navy fast-attack submarine just arrived in Cuba, shortly after a Russian sub showed up there.
• The Los Angeles-class USS Helena is in Guantanamo Bay, while the Yasan-class Kazan is near Havana.
• US and Western officials have long expressed concerns over Russia's Yasan-class boats.

A US Navy nuclear-powered attack submarine arrived in Cuba on Thursday, the Pentagon revealed, putting the American combat vessel in the Caribbean nation at the same time as one of Russia's most formidable subs.

US Southern Command said the fast-attack submarine USS Helena is presently in Guantanamo Bay as part of a routine port visit while conducting a "global maritime security and national defense mission" through SOUTHCOM's area of responsibility.