The Invasion of Poland was the German Poland Campaign, which began on September 1, 1939. It was codenamed “Operation Case White”, Unterrnehmen Fall Weiss in German. The German invasion of Poland started World War II. It was also carried out by the Soviet Union, with whom Hitler had signed a non-aggression pact which contained a secret clause that divided Poland in two halves, a German zone and a Soviet zone.
The German plan for the invasion of Poland had been devised by General Franz Halder, chief of the general staff, and was to be executed by General Walther von Brauchitsch. It called for a mass encirclement and destruction of enemy forces. German units would penetrate Poland from three directions; 1) a main attack on the western Polish border would be carried out by Army Group South; 2) Army Group North would start a second route of attack from Prussia; 3) a third assault would be carried by allied Slovak units from Slovakia. The infantry would be supported by German tanks and small numbers of truck-mounted infantry to assist the rapid movement of troops and concentrate on localized parts of the enemy front to isolate segments of the Polish army, surrounding, and annihilating them.
The Invasion of Poland was initiated at 08:00 hours, on September 1, 1939, when German troops poured over the Polish border near the town of Mokra, starting the Battle of the Border as 62 German divisions supported by 1,300 aircraft broke loose into Poland. It had been preceded by German air and naval attacks; at 04:40 hours on September 1, the Luftwaffe had bombed the Polish town of Wielun and the German battleship Schleswig-Holstein opened fire on the Polish garrison of the Westerplatte Fort, Danzig. These attacks were the first military engagement of World War Two.
The Luftwaffe destroyed all road and rail junctions, as well as concentrations of Polish troops. Towns and villages were heavily bombed, too. Fleeing mass of terror-stricken civilians came out onto the roads which were blocked by people who tried to run away from the bombing, hampering the flow of Polish military reinforcements to the front.
On September 3, General Günther von Kluge reached the Vistula river in the north penetrating 10 kilometers of Polish territory while Georg von Küchler approached the Narew River. On September 5, after crossing the Warta river, Walther von Reichenau’s armored division took the town of Kielce, and by September 8, one of his armored corps had reached the outskirts of Warsaw. In the first week of war the Germans had advanced 145 miles. On September 9, Heinz Guderian led his 3rd Army tanks across the Narew, attacked the line of the Bug River, and encircled Warsaw. All the German armies made progress in fulfilling their parts of the Fall Weiss plan. The Polish armies broke up into loose fragments incapable of launching coordinated counterattacks. Some Polish units began to retreat while others were launching isolated attacks on the nearest German columns.
Polish units withdrew from Pomerania, Greater Poland and Silesia in the first week of the invasion. On September 9, the Germans launched an assault on Warsaw, which had been bombed since the beginning of the war, laying siege to the city. On September 10, the Germans were tightening their encirclement of the Polish Army west of the Vistula. Then, the Polish commander-in-chief, Marshal Edward Rydz-Smigly, ordered a retreat to the southeast.
Near the Bzura river west of Warsaw, the largest and fiercest battle of the Poland campaign was fought from September 9 to September 19, 1939. Polish armies that retreated from the border area of the Polish Corridor, attacked the advancing German 8th Army flank, but these attacks failed. German air power played a key role during the battle. The Luftwaffe’s air raids destroyed what remained of Polish resistance in an awesome demonstration of air power. German Stukas destroyed the bridges across the Bzura River. Then, the Polish forces were scattered fragments out in the open, isolated from one another, as wave after wave of German planes hit them hard.
Eager to grab their allotted share of the country, Soviet forces attacked Poland on September 17. The Soviet invasion convinced the Polish government that the war in Poland had been lost. Nevertheless, the Polish government refused to negotiate a peace with Germany, ordering all units to evacuate Poland and reorganize in France. Warsaw held out until September 28. The Modlin Fortress north of Warsaw surrendered on September 29 after an intense battle.
Invasion of Poland 1939