[Russia navy submarine]Scanpix Denmark/Sarah Christine Noergaard via Reuters * Russian submarine activity in the Atlantic and around Europe increased 50% between 2018 and 2019, the head of US European Command said Tuesday. * That is only the latest warning from a US military commander about Russian subs, which US and NATO navies believe are getting more sophisticated and better armed. * Visit Business Insider's homepage for more stories. Russian submarines are getting more active, and the US isn't always able to keep track of them, the head of US European Command said Tuesday. Air Force Gen. Told Wolters, who is also NATO's Supreme Allied Commander Europe, told the Senate Armed Services Committee that his command saw a marked increase in Russian submarine activity between 2018 and 2019.SEE THE REST OF THE STORY AT BUSINESS INSIDERNOW WATCH: Everything you've ever wanted to know about life on a US Navy submarine SEE ALSO: * US troops are heading north to train on what could be the next World War battlefield * The US and Greece held a live-fire military exercise at the foot of Mount Olympus * Pompeo says the West is winning. The rest of the West isn't so sure SEE ALSO: THE MILITARY'S 'WAR FOR TALENT' IS AFFECTING WHAT THE NAVY'S FUTURE SHIPS WILL LOOK LIKE