The Polish Crisis came to a head in August. The Germans placed more pressure on Poland over Danzig and the corridor, with civil disturbances taking place. The Poles stood firm, bolstered by assurances of support from France and Britain. On August 12-13, Italian Foreign Minister Count Galeazzo Ciano met with Hitler to discuss a diplomatic solution. Italy did not want its ally going to war; the nation was still recovering from its campaigns in Albania, Ethiopia, and Spain and was not ready to fight the French and British. The Italian military needed time to modernize its forces and did not expect to be ready until 1942. Hitler, confident in his course, would not be swayed. Ciano felt the Germans had breached their agreement, but there was little to be done.
On August 17, the Nazis enacted their scheme to justify invasion. The Wehrmacht supplied Polish Army uniforms to operatives commanded by senior SS officer Reinhard Heydrich to create incidents of Polish attacks on German soil. Hitler addressed his military leaders about the issue on August 22, admitting an incident would be “arranged.” The morality of such an act was irrelevant; only victory mattered. He thought it unlikely the British and French would intervene, and if they did they could not reinforce Poland directly. If war came, Germany would win. Hitler also mentioned the impending treaty with the Soviets, which was signed the next day. The speech ended with a statement of belief that the Wehrmacht could carry out any order successfully.
When the Molotov-Ribbentrop Pact became public on August 23, it seemed war was inevitable. Hitler ordered the attack to begin on August 26. The next day the British sent Poland a written guarantee that Britain and France would come to its aid if Germany invaded. When he learned of the move, Hitler rescinded his attack order and engaged in a last-minute move to forestall the involvement of the Western Allies. He promised to respect the current borders with France and to support the British. This offer did not impress either nation, which had no reason to trust such promises. Negotiations were essentially broken off.
Nazi Germany Declares War on Poland
On August 31, Hitler signed the order for the Nazi invasion of Poland, to begin the next morning at 4:45. At 8 pm on the night before the invasion, Germans in Polish uniforms “captured” a German radio station in Silesia. A broadcast in Polish announced an attack on Germany. Soon German police subdued the “attackers.” Casualties were found dressed in Polish uniforms, but they were actually condemned German criminals. Within hours the full might of the Wehrmacht was thrown against the Poles.
When the invasion of Poland came, the Wehrmacht pursued a plan to envelop and destroy the Polish Army west of the Vistula and Narew Rivers. The main blow came from Army Group South under Generaloberst Gerd Von Rundstedt, striking northeast out of Silesia toward Warsaw. A secondary thrust would come from occupied Czechoslovakia to handle Polish troops in Galicia. Generaloberst Fedor von Bock’s Army Group North would strike east through the Polish Corridor to link with East Prussia. That done, Bock would then advance on Warsaw from the north.
Polish plans were for a forward defense in western Poland. This was required; much of the Polish Army was made up of ethnic Poles who lived in the western part of the nation. They would need time to mobilize. A quick defense would hopefully also draw Britain and France into the war sooner. It was an imperfect plan, as it allowed the Poles to be decisively engaged early in the fighting. Polish units would also have to cover more territory than was prudent. Combined with Allied underestimation of Germany’s new army and tactics, it was a recipe for defeat, though in fairness the Poles were in a bad position no matter what plans they enacted.
Despite all the mobilizations and signs, the attack was a tactical surprise for the Poles. The Luftwaffe commenced bombing while the old German battleship Schleswig-Holstein began shelling the Polish fortress at Westerplatte. The Polish Navy was attacked and would be effectively destroyed within a few days. The advancing ground troops swept aside a few Polish patrols and border guards and moved into Poland itself. Paramilitary troops from both sides engaged in a vicious struggle for Danzig.
The Polish Corridor was defended by two infantry divisions and a cavalry brigade. The German 4th Army attacked, and the Polish cavalry fought a series of delaying actions, including a raid that resulted in a cavalry charge against a surprised German infantry battalion. They were only beaten off with the arrival of a few armored cars. The next day Italian war correspondents were brought to the scene. They reported being told the Polish cavalrymen had been killed while charging German panzers. The story took hold of the popular imagination until it became an accepted reality, but the tale is just a myth.
As 4th Army hit the Polish Corridor, 3rd Army advanced out of East Prussia toward Warsaw. Two corps attacked but ran into the Mlawa Line, a fortified zone guarding the obvious route of attack. The Germans tried to outflank the position, but swamps secured both flanks, bogging down the effort after several assaults failed. The Polish Mazowiecka Cavalry Brigade met the German 1st Cavalry Brigade along the Ulatkowka River. Engagements between mounted patrols soon led to heavy dismounted combat. By sunset of the first day of the war, 3rd Army was stopped cold.
Making the main effort, Army Group South saw extensive action, particularly with its 8th and 10th Armies in Silesia. They intended to strike against the Polish Armies Lodz and Krakow, get over the Warta River, and cut off enemy forces in western Poland. Afterward they would advance on Warsaw. These two Wehrmacht formations contained many of the German armored and mechanized divisions.
Initially fighting was light since the Polish defenses were 20 miles behind the border. The worst fighting took place when the 4th Panzer Division attacked the Wolynska Cavalry Brigade at the village of Mokra. The horsemen were assisted by an armored train, while the Germans had trouble coordinating their tanks and infantry. A Stuka raid succeeded in destroying Polish supplies and killing many of their horses, but the cavalrymen held firm. High casualties forced them to finally retreat at sunset, with German tanks hounding them. Meanwhile, Army Krakow suffered badly, its 7th Infantry Division being cut off and overwhelmed by several German divisions. The fortified city of Katowice fared better, however, limiting German success. The rear areas were threatened by guerrilla units of ethnic Germans formed by German intelligence before the war.
Advancing from Slovakia, the 22nd Panzer Corps got around the Polish border units manning the Dunajec Line, forcing Army Krakow to deploy its 10th Mechanized Brigade. The attack was stopped only when the Polish 6th Infantry Division was also committed. Two German mountain divisions attacked across the Carpathian Mountains against Army Karpaty, but the terrain kept them from making any gains.
The Luftwaffe tried to destroy the Polish Air Force on the ground, but most of it was already dispersed to auxiliary fields. Despite more myths, only 24 Polish combat aircraft were destroyed on the ground during the entire campaign, though many trainers and unserviceable planes were destroyed. The Luftwaffe also hit railways and important roads in preplanned attacks. Also contrary to legend, the Germans were not yet capable of hasty close air support missions. In the days to come more planned targets were hit, and Polish troop movements were successfully interdicted, hampering the mobilization of reserves. A few close air support missions were attempted late in the campaign.
A bombing attack on Warsaw took heavy losses to the fighters of the Polish Pursuit Brigade on the first day of the war, but Luftwaffe numerical superiority enabled repeated strikes and by September 6 the Polish unit had lost 70 percent of its fighters, forcing its withdrawal. The rest of the Polish fighter strength was used up in the skies over the main fighting, inflicting at least 126 losses on the Germans. Polish bomber crews flew bravely against the advancing German armies but likewise suffered terribly for little effect.
Back in the north, the Wehrmacht continued advancing along the corridor while Polish forces withdrew southward, leaving the Westerplatte garrison cut off. In the Tuchola Forest, the 3rd Panzer Division managed to cross the Brda River. Two German divisions also advanced west down the corridor from East Prussia, nearly trapping the Polish units between them. Only one Polish division was able to escape the encirclement on September 3. The Germans kept up pressure on the Mlawa Line, finally starting to outflank it. The beleaguered Polish cavalry was reinforced with the 8th Infantry Division but could not hold the line any longer. By the next day the Mlawa defenders and the remaining Poles not encircled in Pomerania were ordered to withdraw to the Vistula Line.
During the night of September 2, the Polish Podlaska Cavalry Brigade conducted a raid into East Prussia, the only Polish attack on German territory. It withdrew after some skirmishes with German militia. The Polish 20th Infantry continued manning the Mlawa Line to allow their comrades to withdraw. It was soon surrounded but continued to resist. Army Modlin tried to hold at the town of the same name, but German river crossing operations threatened the Polish position. After a failed counterattack, the Poles withdrew again across the San River. Another Polish garrison tried to delay the Germans at Modlin but was also surrounded by the advancing Nazis.