There were also some missions which produced an almost 100% casualty rate amongst the Blenheims. One such operation was mounted on 13 August 1940 against a "Luftwaffe" airfield near Aalborg in north-western Denmark by twelve aircraft of 82 Squadron. One Blenheim returned early (the pilot was later charged but was killed on another operation before a court martial was held); the other eleven, which reached Denmark, were shot down, five by flak and six by Bf 109s. Blenheim units had also been formed to carry out long-range strategic reconnaissance missions over Germany and German-occupied territories. In this role, the Blenheims once again proved to be too slow and vulnerable against "Luftwaffe" fighters and they took constant casualties.