According to Simon MacKenzie, "callous self-interest and a desire for retribution played a role in the fate" of German prisoners, and he exemplifies by pointing out that sick or otherwise unfit prisoners were forcibly used for labour, and in France and the Low Countries this also included work such as highly dangerous mine-clearing; "by September 1945 it was estimated by the French authorities that two thousand prisoners were being maimed and killed each month in accidents."[19][20]