Infantry was the most numerous and one of the most important formations in the Polish armed forces in the interwar period and during the September campaign. During the September campaign of 1939, the basic operational unit of the Polish infantry - as in almost every European army of that time - was a division, which, after mobilization, was to reach approx. 16,500 soldiers. Its basic strike force was three infantry regiments, supported by anti-aircraft and anti-tank artillery (27 37 mm cannons in full time) and light and heavy artillery (24 or 12 75 mm cannons in full time, 12 or 24 100 mm cannons, 3 105 mm cannons and 3 howitzers 155 mm). It is worth adding that the Polish infantry division showed many shortcomings compared to the German division. First of all, it had fewer machine guns and, above all, light and heavy artillery. Moreover, in the case of the Wehrmacht, the latter were significantly better equipped with motor vehicles, which improved their mobility and had much better means of communication and communication. For example: the German infantry division had 938 full-time cars, while the Polish - only 76 motor vehicles! This translated into the effectiveness of both formations on the battlefield, as well as their firepower and mobility.
The officer corps of the Polish Army, shortly after Poland regained independence, was highly heterogeneous and inconsistent. This is not surprising, considering that it was made up of officers previously serving in the Austro-Hungarian, German and Russian armies, as well as officers serving in the Polish Legions. With time, however, in the 1920s and 1930s, this corps began to form a coherent and doctrinally uniform whole, constituting an important element of the elite of Polish society in the interwar period. Military education was developed, and officers were sent to appropriate foreign courses - primarily to France, allied with Poland. It is often mistakenly assumed (especially in Anglo-Saxon literature) that under the influence of the latter, the Polish military doctrine adopted a predominantly defensive attitude, which is quite an abuse. In its essence, the Polish military doctrine of the interwar period was based rather on the experiences of the war of 1919-1921 and placed considerable emphasis on maneuver, pace of operations and counter-attacks. Another thing is that the technical means to implement these assumptions were often lacking. It is worth adding that during the Second Polish Republic, the Polish officer corps was divided into junior officers, senior officers, staff officers and the generals. The highest rank in the entire army was the Marshal of Poland, which Edward Rydz-Śmigły had during the September campaign. During the September campaign, the Polish officer corps performed differently. On the one hand, it is possible to point to the wrong, missed war plan developed by Marshal Rydz-Śmigły, the shameful attitude of General Stefan Dęb-Biernacki, and on the other - considerable professionalism and courage of the later generals of Stanisław Maczek or Stanisław Sosabowski.