In September 1939, following the German invasion of Poland, the city was occupied by Germany and made part of the General Government. The Polish and Jewish population were subjected to various crimes. Poles expelled in late 1939 by the Germans from Złoczew, which was directly annexed by Germany, were deported to Sandomierz. Others were conscripted for forced labour and many were sent to labor camps. The largest mass arrests of Poles, including teachers, local officials and activists, were carried out in March 1940. In June 1940 in Brzask Forest, Germans murdered 760 Poles as part of the German AB-Aktion in Poland directed to exterminate Polish intelligentsia. Bodies were buried in unnamed mass grave. That was the largest massacre in the Kielce Region. Poles were then held in the local prison and deported to German concentration camps. At the same time, the nearby village of Góry Wysokie was the site a massacre of 117 Poles from the region. Despite this, the Polish underground resistance movement was active in Sandomierz, and in late 1940 it even launched a secret printing house in Sandomierz and issued the Polish underground newspaper "Odwet", which was also distributed to nearby villages. In March 1942, the Germans carried out mass arrests of around 150 members of the Polish resistance. Among those arrested was local Polish writer Roman Koseła, one of several Polish writers murdered in the Auschwitz concentration camp.