the area of Częstochowa, the 7th I.D. (General Janusz Gąsiorowski) was placed, with its right wing supported by the Kraków Cavalry Brigade of General Zygmunt Piasecki. The remaining units were divided into two operational groups. Operational Group Silesia (under General Jan Jagmin Sadowski) was made of the 23rd I.D. (Colonel Władysław Powierza), together with the 55th (reserve) I.D. (Colonel Stanisław Kalabiński), and soldiers manning the Fortified Area of Silesia. Operational Group Bielsko (under General Mieczysław Boruta-Spiechowicz) was made of the 21st I.D. (General Józef Kustroń), and the 1st Brigade of Mountain Infantry (Colonel Janusz Gaładyk). This group was located in the area of Żywiec, Chabówka, and Bielsko-Biała. Furthermore, in the area of Pszczyna was the 6th I.D. (General Bernard Mond), and in the area of Kraków, the 10th Motorized Cavalry Brigade (Colonel Stanisław Maczek). Kraków Army's tasks were as follows: to defend Upper Silesia, to protect the general direction towards the city of Kraków from southwest, to defend the strategic rail line from Dąbrowa Górnicza Ząbkowice to Częstochowa, final line of defence was as follows: Fortified Area of Silesia - Mikołów - Pszczyna - Bielsko-Biała - Żywiec. Operational history Battle of the Border Kraków Army fought against German Army Group South, whose units crossed the border on September 1, 1939, at 4 a.m. In central part of the front, German 10th Army advanced, attacking in the sector from Tarnowskie Góry to Wieluń. North of the 10th Army was the 8th Army (advancing towards Sieradz and Łódź), and in the south was and the 14th Army, advancing towards Kraków. On September 1, the Wehrmacht failed to cause a breach Polish positions, but it was obvious that the Germans tried to bypass Fortified Area of Silesia, attacking both north and south of the fortifications. As early as the night of September 1/2, Polish situation became difficult, as the 7th I.D., operating near Częstochowa, found it hard to halt the advance of the panzers of the XVI Panzer Corps, which fought their way into central Poland. This division was located some 40 kilometers away from other Polish units; close to it was the Volhynian Cavalry Brigade, which itself was attacked by the Germans in the Battle of Mokra. On September 2, German 1st Panzer Division bypassed Częstochowa north of the city, and supported by the Luftwaffe, managed to cross the Warta river. At the same time, Kraków Cavalry Brigade was attacked by the