At the end of August 1939 the Germans took concentration camp prisoners dressed as German soldiers to the Polish frontier and had them shot. Their bodies were shown to journalists to make it seem that Poland was attacking Germany. The Germans then made a massive surprise attack on Poland. Within ten days the Polish army had been defeated and before the end of the month an independent Poland no longer existed.

The Polish infantry armies were organised for the World War One method of fighting and were placed well forward near the frontiers. There were very few tanks to face eight German motorised divisions and six Panzer divisions, supported by dive-bombers. Most of the Polish air force was wiped out in the first few days. Terror bombing filled the roads with civilian refugees, creating massive confusion. German spies living in Poland --supplied information to Germany and German bombers attacked and paralysed the Polish command headquarters.

The first moves of the German army are the beginning of a great pincers action. General von Rundstedt commanded the German armies in the south. They broke through the Polish defences, led by the 10th Army, which had most of the tanks. The Polish infantry fought fiercely but were out-flanked and left behind by the advances of the panzers. The mechanised forces, closely, supported by Stuka dive-bombers, swept kilometres ahead of the German infantry. The 10th Army pushed northwards towards the capital, Warsaw, and the Poles were cut off from escape across the River Vistula. They then made strong attacks on the Germans near Lodz. Cavalry charged German tanks with lance and sabre thinking that they were fakes made of wood and canvas. Polish troops were surrounded in great pockets in the centre of the country. From the north General Gunderian, creator of the panzer divisions, drove his tanks through to Brest Litovsk and met other panzers from the South in a second pincers movement.

On 17 September, when it was clear that the Germans had defeated the Poles, the Russians then invaded Poland from the east. Poland was conquered in eighteen days and Warsaw fell by the end of September.

The Poles had confidently expected a French attack on Germany in the west but the French were slow to assemble their troops and the campaign was virtually over before their armies were ready to move. Hitler was impressed by the success of blitzkrieg methods. The Germans took 650 000 Polish prisoners; their losses were 45 000. However the infantry armies had done much of the fighting and the panzers had not played such an important role as they did in later campaigns. As agreed in the Nazi-Soviet Pact, the Soviet Union took half of Poland. In both parts of Poland systematic killings and deportations were soon started.