During the German invasion of Poland, which started World War II in September 1939, Szczucin was the area of several skirmishes between retreating units of the Kraków Army, and the advancing Wehrmacht. On September 12, 1939, German soldiers carried out a massacre of around 40 Polish prisoners of war and around 30 Polish civilian refugees (see also "Nazi crimes against the Polish nation"). Altogether, 70 Poles were murdered, and this tragedy is commemorated by a monument. During the German occupation, Szczucin was a center of the Polish resistance movement. In 1943, soldiers of the Jędrusie resistance organization executed here an officer of the Blue Police. In late 1944, Germans ordered evacuation of all Szczucin's inhabitants, because they prepared defensive positions along the Vistula.