On the morning of September 1, the Luftwaffe struck at the Polish airfields, destroying nearly all of the planes before they could get off the ground. It then set about systematically disrupting the railroads and lines of communications. Before the clay ended, the Polish leadership was helpless. Mobilization could not be completed, and large-scale troop movements were impossible.
The first phase of the campaign, the breakthrough on the borders, ended on September 5. By September 7, the point of the Tenth Army was 36 miles southwest of Warsaw. The Eighth Army on the left had kept pace, executing its mission of protecting the flank, while the Fourteenth Army on the right had captured the Upper Silesian industrial area. By September 5, the two armies in Bock’s Army Group North had cut across the corridor and had begun turning to the southeast, and two days later elements of the Third Army reached the Narew 25 miles north of Warsaw. The Poles fought gallantly, but cavalry was no match for tanks. On September 6, the Polish government left Warsaw for Lublin; later it moved close to the Rumanian border, which it crossed on September 16.
The second phase of the campaign completed the destruction of the Polish armed forces. According to the German plan, this was to have been accomplished in a single giant encirclement west of the Vistula. After intelligence reports indicated that the government and large numbers of Polish troops had fled across the river, the plan was changed in accordance with Bock’s earlier proposals. The OKH, on September 11, ordered a second deeper envelopment, reaching eastward to the line of the Bug ( Western Bug) River.
In the meantime, the closing of the inner ring at Warsaw had created the first and only genuine crisis of the war. The Polish Poznan Army, bypassed in the first week, at the beginning of the second week felt the German pincers closing behind it. Turning around, it attempted to break through to Warsaw. For several days after September 9, staffs of the German Eighth and Tenth armies were put to a severe test as they swung some of their divisions around to meet the attack coming from the west. The Poles did not break through, however, and the ring gradually closed. On September 19, the Poznan Army, numbering 100,000 men, surrendered, ending the last resistance by a major Polish force.
The most spectacular feature of the outer envelopment was the advance of Gen. (later Col. Gen.) Heinz Guderian’s panzer corps from East Prussia across the Narew to Brest (Brest-Litovsk), which it took on September 17. Elements of the corps then continued past the city to make radio contact with the Tenth Army spearhead at Wlodowa, 30 miles to the south.
The war ended for all practical purposes on September 19. The fortress at Lwow ( now Lvov ) surrendered two days later. Warsaw itself held out until September 27. Modlin capitulated on September 28, and the last organized resistance ended on October 6, when 17,000 Polish troops surrendered at Kock. In the whole campaign the Germans took 694,000 prisoners, and an estimated 100,000 men escaped across the borders into Lithuania, Hungary, and Rumania. The Germans lost 13,981 killed and 30,322 wounded; Polish losses will probably never be known.