An unnamed US ballistic-missile submarine arrived in Gibraltar on Monday amid persistent tensions with Iran. US Navy courtesy photo

The Pentagon shared a photo of an Ohio-class ballistic-missile submarine docked in Gibraltar.

The Navy said the submarine's visit demonstrates US capability and commitment to NATO allies.

Sharing the location of a nuclear-armed submarine sends a clear message to adversaries.

The US military rarely discloses the locations of its deployed ballistic missile submarines , the naval arm of its nuclear might. When it does, it's often meant to send a message.

On Monday, the US Navy's Sixth Fleet shared a photo of an Ohio-class ballistic-missile submarine docked in Gibraltar, writing that the unnamed sub's visit to the British territory off the coast of Spain "demonstrates US capability, flexibility, and continuing commitment to its NATO allies."

The Navy release didn't mention Iran or the ongoing conflict, but the appearance of a "boomer" submarine — that's designed to carry…