The German invasion of Poland began on the 1 September 1939. The invasion began World War II. The Bf 110 "Zerstörergeschwader", "Zerstörergeschwader" 76 (ZG 76—76th Destroyer Wing) and ZG 26 distinguished themselves in the fighter escort role as the long-range bomber pilots from "Kampfgeschwader" 27 attacked Warsaw airfields to destroy the Polish Air Force. JGr 102, under the command of "Hauptmann" Gentzen claimed 28 Polish aircraft in aerial combat and a further 50 on the ground. Colonel Stefan Pawlikowski's "Warsaw Pursuit Brigade" resisted fiercely but lost 17 percent of its fighting strength on 1 September which rose to 72 over the next five days. The unit may have claimed as many as 29 in the air and 78 on the ground. One of JGr 102's missions was providing fighter escort for Ju 87 "Stuka" dive-bombers in the Bombing of Wieluń. No Polish aerial resistance was encountered. Gentzen claimed seven victories in two days: on 3 September he shot down a PZL.37 Łoś medium bomber and two PZL P.11 fighters. The next day he claimed four PZL.23 Karaś attack-bombers. On the 3rd, the Polish Air Force flew 90 sorties in the Częstochowa-Radomsko area as bombing intensified. The Poles did lose nine P.23s in the area as JGr 102 [I./ZG 2] and I./JG 76 were unleashed on combat patrols.