Before dawn on 1 September 1939 Germany attacked Poland without a declaration of war. The old battleship Schleswig-Holstein opened fire on the Polish depot at Westerplatte in Danzig harbor, German bombers struck the town of Wieluń, and German armies crossed the border from the north, the west and the south. It was the start of the Second World War in Europe. This page is a short guide to the day; the battles themselves are told in full in our own articles, linked below.
The first shots
The National WWII Museum notes that on the night of 31 August the Germans staged a fake attack on the radio station at Gleiwitz, on their side of the border, and that by the next morning Hitler was already using it to justify the invasion. The Schleswig-Holstein, moored in the harbor channel opposite Westerplatte, began the bombardment before dawn. The museum gives the time as 4:43 a.m., while the Polish Institute of National Remembrance (IPN) dates the German attack on Poland to 4:45.1 › Gleiwitz incident, 1939
The garrison of the Military Transit Depot, a little over 200 men under Major Henryk Sucharski and his deputy Captain Franciszek Dąbrowski, held out until 7 September. Their stand is told in our article on Westerplatte.2
Wieluń, a town near the border with no Polish troops or air defenses, was bombed the same morning, and the museum says it was flattened on the first day. The time is disputed: Polish tradition says 4:40, a few minutes before Westerplatte, but the IPN historian Grzegorz Bębnik argues the raid began at 5:40, because the earlier figure wrongly assumed German summer time. The IPN investigation counted at least 18 dead in the town hospital and at least 109 other residents, Poles and Jews, while other estimates run as high as 1,200.3
An invasion from three sides
Army Group North attacked from Pomerania and East Prussia, and Army Group South from Silesia, with a smaller thrust from Slovakia. The size of the force is given differently. Britannica counts sixty-two divisions supported by more than 1,300 aircraft and some 1,250,000 German troops in the whole campaign, while the National WWII Museum gives about 1.5 million men, 2,750 tanks and 2,315 aircraft. Poland could nominally field about a million men, but many were still mobilizing when the attack came; Britannica puts the Polish army at 800,000.4
On the first day Polish troops fought along the whole frontier. At Mokra, according to the dzieje.pl history portal, the Volhynian Cavalry Brigade under Colonel Julian Filipowicz held off the German 4th Panzer Division for most of the day. See our article on Mokra, and the defense of the fortified line north of Warsaw in our article on Mława. The Hel peninsula, the last Polish stronghold on the coast, is covered in our article on Hel.5
What followed
Britannica notes that Britain and France declared war on Germany on 3 September, which did nothing to help Poland in the field. The Poles struck back on the Bzura from 9 September, told in our article on the Bzura, and on 17 September the Soviet Union invaded from the east under the secret terms of its pact with Germany. Warsaw surrendered on 27 September, and the last Polish field force laid down its arms after the battle of Kock in early October: Britannica ends the campaign on 5 October, the museum on 6 October. The last battle is in our article on Kock.6
