Carrying gas masks became routine for adults and children during the Second World War. But this collection of photographs shows it was commonplace for dogs to be equipped with breathing apparatus' too. The array of fascinating pictures collected by blog Retronaut demonstrate how often canines were called upon to help with the war effort. Dogs were fitted with gas masks to avoid the deadly fumes and fought for both sides during the Second World War. The black and white photographs show a number of dogs in a range of situations, equipped with masks and fighting for both sides in the war.