victory on 1 June during the Battle of Dunkirk. He was credited with the destruction of a Royal Air Force (RAF) Supermarine Spitfire at 12:42 over the combat area of Dunkirk. The next day, II. Gruppe again fought over the Dunkirk battle zone and Borris claimed his second aerial victory. At 09:10, he claimed a Spitfire which came from either No. 66, No. 266 or No. 611 Squadron. During the Battle of Britain, Borris was credited with two aerial victories on 13 August, a day that was codenamed Adlertag (Eagle Day) by the Luftwaffe. II. Gruppe made contact with Hawker Hurricane fighters from No. 56 Squadron over Maidstone and for the loss of one Bf 109 E-1 shot down, claimed two Hurricanes destroyed, both of them by Borris between Maidstone and Detling. On 6 September, he claimed another Hurricane shot down. This Hurricane was a No. 501 Squadron aircraft ans was claimed at 09:55 near Folkestone. Borris claimed his final aerial victory of the Battle of Britain on 25 October. On an escort mission for fighter bombers from II. Gruppe of Lehrgeschwader 2 (LG 2—2nd Demonstration Wing), Borris claimed the destruction of a No. 603 Squadron Spitfire near Maidstone. Testing the Fw 190 On 5 March 1941, Borris, at the time the technical officer of II. Gruppe, and Oberleutnant Otto Behrens, the Staffelkapitän of 6. Staffel, were sent to the Luftwaffe main testing ground () for new aircraft designs at Rechlin for operational testing of the then new Focke Wulf Fw 190. Both Borris and Behrens were prewar aircraft mechanics and headed a team of 30 mechanics and engineers. The unit was given six pre-production Fw 190 A-0 fighters for evaluation and conducted numerous test flights and made various suggestions which proved vital to working out all the technical challenges associated with a new aircraft design. The Erprobungsstaffel 190, the operational Fw 190 test squadron, headed by Behrens, was ordered from Rechlin to the Le Bourget airfield near Paris on 1 August. There, they were tasked with training II. Gruppe of JG 26 on the Fw 190 A-1. Borris was transferred to the 6. Staffel which at the time was commanded by Oberleutnant Walter Schneider and was based at an airfield in Moorsele Belgium. 6. Staffel was the first operational unit to be equipped with the Fw 190. By September, the entire II. Gruppe was flying the Fw 190. On