Many German radio messages were encoded using the Enigma machine and other enciphering techniques and the codes were changed frequently. A team of code breakers stationed at Bletchley Park worked to break codes as quickly as possible to provide advance information on German plans and troop movements. British military intelligence code-named this information Ultra intelligence as it could only be provided to the top level of commanders. The Enigma code used by Field Marshal Gerd von Rundstedt, "Oberbefehlshaber" West (Supreme Commander West; OB West), commander of the Western Front, was broken by the end of March. German intelligence changed the Enigma codes right after the Allied landings of 6 June but by 17 June the Allies were again consistently able to read them.