On the 1st September 1939, German forces invaded Poland in a move that was to trigger the Second World War. Germany had already removed the threat that the USSR might respond aggressively by signing the Nazi-Soviet Pact a week earlier. Furthermore, the Nazis manufactured a situation in Poland to claim that their military response was an acting of self-defence.
During the night of the 31st August, Nazi SS troops dressed in Polish uniforms and staged an attack on the Gleiwitz radio tower in Upper Silesia. This ‘false flag’ operation was part of a wider series of staged attacks by Germans and German property called Operation Himmler that was designed to make it appear that Poland was exercising aggression against Germany.
Just hours after the Gleiwitz incident, at 4.45am on the 1st September, the first of approximately 1.5million German troops launched their attack on Poland. The effective encirclement of Polish forces by launching the coordinated attack at the same time from the north, south and west. The attack from the south came across the border with Slovakia, which had declared its independence in March under pressure from Hitler.
Known as the Battle of the Border, the three-pronged ground attack was supported by air raids that targeted Polish cities. It took just 5 days for troops on the ground to force the Polish army to retreat to their secondary defensive lines. The USSR joined launched its own invasion from east on the 17th September, and this crushed Polish hopes of victory.
The Polish government refused to surrender to Germany and instead evacuated the country and regrouped in Allied countries.