The second sub-camp, Sisak II, was reserved for those who were deemed unfit for forced labour. Its operators euphemistically referred to it as a "reception center for children and refugees" or the "shelter for children refugees". According to the historian Joseph Robert White, the first 1,200 children arrived from the Mlaka sub-camp on 29 July 1942, with subsequent transfers from Jasenovac V (Stara Gradiška) and Jastrebarsko taking place in August. According to the historians Paul R. Bartrop and Eve E. Grimm, Sisak II was officially established on 3 August 1942, following the Kozara Offensive (). The first group of 906 children arrived at Sisak II on 3 August, according to Bartrop and Grimm, with an additional 650 children arriving the following day, and a third group of 1,272 on 6 August.