The German military machine that launched this campaign was the product of years of careful planning and preparation that had begun almost immediately after Adolf Hitler's rise to power in 1933. Despite the restrictions imposed by the Treaty of Versailles, which had limited Germany to a small professional army and prohibited the possession of tanks, aircraft, and other modern weapons, German military leaders had never abandoned their commitment to rebuilding their nation's military power. Through secret training programs, technological development disguised as civilian research, and careful study of military innovations from other nations, the German armed forces had prepared for the day when they could once again project power beyond their borders.
The Polish campaign revealed the devastating effectiveness of German military innovation and planning. Traditional military wisdom had emphasized the importance of continuous front lines, methodical advances, and the gradual wearing down of enemy resistance through attrition. The German approach rejected these conventional concepts in favor of rapid penetration by combined arms forces that could bypass enemy strongpoints and disrupt command and control systems before defenders could respond effectively. Panzer divisions, supported by tactical aircraft and followed by motorized infantry, punched through Polish defensive positions and advanced deep into the country's interior, surrounding and isolating large numbers of Polish troops who found themselves cut off from supplies and communication with their headquarters.