The transport of 31 July 1943 consists of 1563 deportees including 208 children upon departure. 10 deportees escaped during the journey by jumping out of the moving train, but three of them were shot down. This time, as many precautionary measures as possible were taken to avoid the mass escapes.
The 21st convoy left during the day and followed a different route than usual: after Leuven it went to Hasselt and not to Tienen. Moreover, the convoy was escorted to the border by a company of Flemish SS men on guard with the SS police, as well as by German agents of the "Jewish section" as reinforcement for the agents of the order police, who had come from Germany as with each transport according to the ratio of one agent per 40 deportees. The latter were just as numerous as in the previous transport, but it took 3 ½ months to collect them. Since 24 April, the average number of registrations per day on the departure list has dropped to 16.
The 21st convoy arrived in Auschwitz on 2 August 1943. It is eradicated in the same proportion as the previous one: 70%. The 1097 deportees are gassed on arrival in the new installations of the Birkenau extermination center. With the new crematoria and the gas chambers with a higher capacity, it had a real industrial eradication machine tailored to the genocide since spring. 486 deportees from the 21st convoy are admitted to the camp. The captivity will wreak havoc there than with their companions of the 20th convoy.
The survival rate of the convoy is one of the lowest: barely 40 people - only 2.6% - survive the liberation.
Source: The Memorial of the Deportation of the Belgian Jews, page 31.