On 16 December the German High Command ("Oberkommando der Wehrmacht") initiated "Unternehmen Wacht am Rhein" (Operation "Watch on the Rhine"), a land offensive through the Ardennes. The Luftwaffe supported the offensive. JG 77 suffered heavily in the air battles with the RAF Second Tactical Air Force and the US Ninth Air Force and Eighth Air Force. On 23 December 1944 I./JG 77 lost 15 fighters and six pilots killed in exchange for one P-47 Thunderbolt and a B-26 Marauder. In the afternoon, III./JG 77 were engaged by P-47s over Bad Münstereifel and lost 10 Bf 109s destroyed and three damaged along with two pilots killed and six wounded. Only three P-47s were claimed.