Intruder pilots began accumulating personnel successes. One such pilot was Paul Semrau. He claimed his 6th victory on the night of 18/19 June 1941 off Great Yarmouth. Semrau claimed 46 night victories until he was killed by Supermarine Spitfires in February 1945 conducting an unwise daylight test flight. There were successful intruder pilots who did not become high-claiming night fighters. Albert Schulz and Hermann Sommer of 2./NJG 2 claimed several victories over England; Sommer later fought in the Battle of the Mediterranean. Sommer proved intruders a threat to RAF training centres when he accounted for an Airspeed Oxford trainer on 29 April 1941, confirmed through British sources. Wilhelm Beier, another eventual Knight's Cross of the Iron Cross recipient, from 3./NJG 2 claimed two aircraft on two consecutive nights from 5 to 7 July 1941 to reach his 10th victory. Heinz-Horst Hißbach was another that began his career on intruder missions. Heinz Strüning ended the intruder missions with nine victories. Total claims improved from 1940. In 1941, until mid-October, 128 RAF aircraft were claimed against 28 losses. Other sources put German losses at 55 aircraft along with 74 personnel. RAF night fighters carrying Airborne Interception radar were making flights to England hazardous. Hans Hahn of I./NJG 2 became the leading intruder "expert", but was killed in October 1941, shortly before Adolf Hitler ordered a stop to intruder operations. Bomber Command reports list only seven complete losses to intruders and 20 badly damaged aircraft from 1 October 1940 to 31 March 1941.