Operation Cobra is the first expansion to the Pijamas: Omaha miniatures ruleset published in the magazine Vae Victis #116. It covers the offensive launched by the First United States Army seven weeks after the D-Day landings, during the Normandy Campaign of World War II. The intention is to provide simple and quick additional rules to simulate the fierce fighting of Operation Cobra in taking into account the specificities and the constraints of the bocage country.