During the spring of 1944, the fastest and largest operation of Holocaust took place in Hungary. Weeks after the country had been occupied by the Germans, on 16 April, Jewish people who lived in the county were locked up in ghettos. On 14 May, mass deportations of Jews began. On 9 July 1944, in only eight weeks, 437 000 Hungarian Jews were transported in cattle railroad cars to Auschwitz-Birkenau in Poland. Most of them were killed in gas chambers just hours after their arrival.