This was the German bombing of Wieluń in Poland, on the main axis of Generaloberst Gerd von Rundstedt’s Heeresgruppe 'Süd' in 'Weiss' (i) (1 September 1940).
The Luftwaffe started to attack Wieluń at 04.40, five minutes before the naval gunfire bombardment of Westerplatte, which has traditionally been considered the beginning of World War II, and had as its primary target the Wołyńska Brygada Kawalerii.
According to German records, 29 Junkers Ju 87B Stuka dive-bomber of Sturzkampfgeschwader 76 under the command of Hauptmann Walter Sigel took off from Nieder-Ellguth airfield at 05.02 on 1 September 1939, and about 20 minutes later reached Wieluń without encountering any opposition and then dropped 29 1,102-lb (500-kg) and 112 112-lb (50-kg) bombs. Among the first places hit was the hospital, which was marked with red crosses, and where 26 patients and six nurses were killed. All 29 aircraft then flew back to Nieder-Ellguth, where Sigel reported 'no noteworthy observation of the enemy'.
A second wave of 29 dive-bombers of the StG 2, under the command of Major Oskar Dinort, next attacked the town shortly, followed by a third wave of aircraft at about 14.00. In all, 380 bombs totalling some 101,410 lb (46000 kg) had been dropped on the town, hitting the hospital, killing more than 1,200 inhabitants and destroying 70% of the buildings; as much as 90% of town centre had been destroyed.
Later accounts state that there were neither military nor industrial targets in the area except for a small sugar factory in the outskirts of the town. Another historian claims, however, that a Polish cavalry brigade and a Polish infantry division had been located in the town by German reconnaissance during the day before the attack, and from reports of General Alexander Löhr’s Luftflotte IV, Generalleutnant Bruno Loerzer’s 2nd Fliegerdivision, the I/StG 76 and I/StG 77 has come to the conclusion that the attacks had been directed against these military formations and therefore can not be considered terror bombings.
At 13.00 the I/StG 2 attacked this unit, and was followed a few hours later a force of 60 dive-bombers of Hauptmann Friedrich-Karl Freiherr von Dalwigk zu Lichtenfels’s I/StG 77, led by Hauptmann Günter Schwartzkopff. The weather was unfavourable during the day, with very limited visibility and low-altitude fog, and this severely affected many German air operations on the first day of 'Weiss' (i). In the face of increasingly heavy anti-aircraft fire, the dive-bombers inflicted severe casualties on the Polish cavalry brigade, and the Polish advance toward the front was reversed.
On their return flights, four of the five-bombers were shot down by the 36 pułk piechoty Legii Akademickiej, an infantry regiment stationed nearby. Even so, the town of Wieluń was captured by General Johannes Blaskowitz’s 8th Army on the first day of the invasion.