The nazis also tried to exterminate the Sinti and Roma (gypsies). Already before the war, German and Austrian Sinti and Roma were arrested - under pretence of fighting criminality - and deported to Dachau and Buchenwald. From the mid 1930s, men, women, and children were forced to undergo sterilisation. Once the war began, Sinti and Roma in Eastern Europe became victims of large scale executions carried out by the Einsatzgruppen. From all over Europe they were deported to extermination camps. In Auschwitz the notorious camp doctor, Dr. Josef Mengele used Sinti and Roma children for his cruel medical experiments. Until today it is hard ascertain how many Sinti and Roma were murdered during the war: estimates vary from 100,000 to several hundred thousands. On 16 May, 1944, Sinti and Roma were rounded up everywhere in the Netherlands and deported to Westerbork. Three days later a train with 245 Sinti and Roma left for Auschwitz. After the war only 30 returned. Also, after the war, the persecution of Sinti and Roma was much less discussed and written about than the persecution of Jews.