The US Navy has been mocked for posting a photo online of a sailor shooting a rifle with a back-to-front scope, in what social media users said showed America was “going to lose a major war”.

The now-deleted image of Commander Cameron Yaste, the captain of the guided-missile destroyer USS John S McCain, firing a rifle with a back-to-front scope and the lens cap still attached - US Navy.

The Navy’s official Instagram page issued a photo of Commander Cameron Yaste, the captain of the guided-missile destroyer USS John S McCain, shooting a rifle with a backwards-mounted scope.

The image, also sent as an official press release, was captioned: “From engaging in practice gun shoots, conducting maintenance, testing fuel purity and participating in sea and anchor details, the #USNavy is always ready to serve and protect.”

Social media users and other branches of the US military quickly mocked the image, in which Commander Yaste was also using a scope with the lens cap still attached.

The US Marines posted a separate image of a marine holding and firing a rifle correctly.

One user on X joked: “We’re going to lose a major war”, while another said: “Dear U.S. Navy. The scope is on backwards. This is why we have Marines on ships.”

A third added: “Is this a joke or has this guy never fired a rifle before?”

Others pointed out that Commander Yaste was in an unusual stance for target practice, and that his grip was mounted too far to the rear of his rifle.

Mike Collins, a Republican congressman from Georgia, posted an edited photo of a pistol with its barrel on backwards.

The US Navy photograph was deleted and the press release recalled.

A spokesman said: “Thank you for pointing out our rifle scope error in the previous post. Picture has been removed until EMI is completed!”

The Navy defines EMI as “instruction in a phase of military duty in which an individual is deficient, and is intended for and directed towards the correction of that deficiency”.

The caption of the original image from the Defense Visual Information Distribution Service stated that the captain was firing at a “killer tomato”, the nickname for a naval target balloon.

It said he was “observ[ing] the live-fire exercise event” while on on ship “conducting routine operations”.

Commander Yaste attended the Naval Postgraduate School, earning a master’s degree in astronautics, according to his official bio.