The US Navy is putting its submarines on rare public display in a message to Russia's growing undersea force

• The US Navy has announced several visits by its subs to North Atlantic ports in recent years.
• Subs are among the US's most secretive weapons, and announcements about their movements are rare.
• Their growing visibility comes as Russia's own increasingly advanced subs are getting more active.

The US Navy rarely reveals where its submarines are, but it is making those subs more visible in the North Atlantic, demonstrating their presence as US officials warn that Russian submarines are more active and carrying new weapons closer to US shores.