Nazis Move To CurbPossible Fifth ColumnLondon, June 6 (UP)—The Germans, still executing innocent Czechs for the assasination of Rein-hard Heydrich, today were trying to suppress a potential fifth column they fear will stab them in the back the moment an allied invasion begins.Occupation authorities ordered all Belgian commissioned and noncommissioned officers and reserveofficers to register between June 8 and 13. Those failing to do so will be “severely punished,” the Germans said.Thirty more martyrs were shot alPrague and Brunn yesterday, making a total of 297 killed in reprisal for the shooting of Heydrich, number two man of the gestapo.Members of Jacques Doriot’s militant fascist organization demonstrated against Jews last night in Parkand Nice, Prance.In Nice, Doriot’s followers threwbricks through the windows olJewish stores.Russian Bombers Sink Seven German Transports