The rising threat of attacks by frogmen in naval bases caused various anti-frogman techniques to be developed. In the USSR, one of these techniques was guard frogmen sent to stop the attackers. At first these guard frogmen were armed only with knives and AK-type rifles. The rifle was carried in a waterproof case and could be used only on the surface, so the only effective underwater weapon against enemy frogmen was the knife.
