Before German troops invaded Hungary and the government was reformed on March 19, 1944, Hungarian officials opposed the deportation of Jews. But the new administration under Sztojay, who was pro-German, accepted the German requests and started concentrating Jews in ghettos and transit camps before deporting them to Auschwitz-Birkenau. The first two transports left Kistarcsa on April 29, 1944 (1.800 Jews) and Topolya on April 30, 1944 (2.000 Jews). After an interruption of two weeks the main phase of deportations started on May 15, 1944. Until July 9, 1944, 437 402 Jews were deported from Hungary to Auschwitz. Due to the pressure of neutral countries and the Vatican, "Reichsverweser" Horthy forbad any further deportation. Germany was unwilling to risk a conflict with Hungary at that time, and therefore did not undertake any decisive steps. Nonetheless, some few hundred Hungarian Jews from the camp for political prisoners in Kistarcsa arrived in Auschwitz in August.

The arrival of the first two transports were largely prepared. The crematories were carefully renewed, the ovens covered with fire-clay and the chimneys reinforced with iron rings. Behind the crematories, pits were dug, the number of members in the "Sonderkommando" and the cleaning commandos was increased. Despite the enlargement of the number of inmates in these two commandos, it was not possible to handle the mass of people and their goods arriving in the camp.

The average travel time of the Hungarian Jews amounted to at least four days. Since the vans were always overcrowded, people didn't get enough air to breathe, nothing to eat or drink. Many suffocated or died from thirst. Especially little children, old and ill people died under these transport conditions.

Since the transports were too huge, the SS selected many people for the camp and began to send them to be gassed later. Though, the number of gassed people was so high that the crematories were not able to burn all the bodies - they were piled up in the prepared pits and burnt. In oder to accelerate the burning, grooves were dug to which the fat of the braised bodies would flow. The fat was used to pour it over the bodies in order to make them burn even faster. Sadists among the SS-guards enjoyed themselves by throwing living kids or old women into the braising fat or the fire. The relatives of the deportees and the rest of the Hungarians who noticed the disappareance of so many people, were calmed down by forcing the Hungarian Jews to write post-cards saying: "I'm fine." The sender-address was purely fictional: Labour camp Waldsee. It only existed in the fantasy of the camp-Gestapo. Even those people, who dircetly had to march to the gas chamber, received such cards in the dressing-room of the crematories with the order to write to their homes.