Germany invaded Poland on 1 September 1939 starting World War II in Europe. ZG 76 had been stationed at the Polish border prior to the invasion. Gollob scored the first of his aerial victories over Poland on 5 September 1939, shooting down a PWS 56 (Podlaska Wytwórnia Samolotów—Podlasie Aircraft Factory) biplane. He also flew ground support missions, attacking an airfield and destroying several aircraft on the ground. On 21 September 1939, Gollob was awarded the Iron Cross 2nd Class (). Following the campaign in Poland, ZG 76 was moved to Germany for defensive operations. The 1. "Gruppe" of ZG 76 first relocated to the Stuttgart area on 29 September 1939 to defend the western border against the French and British, who had declared war on Germany on 3 September 1939. From early October to mid-December, I. "Gruppe" operated from airfields in the Stuttgart and Ruhr regions before relocating north to Jever on 16 December 1939. There, on 18 December 1939, Gollob claimed his second aerial victory over a Royal Air Force (RAF) Vickers Wellington bomber in what became known as the Battle of the Heligoland Bight. During the battle, he shot down and killed Squadron Leader Archibald Guthrie, of No. 9 Squadron.