German forces occupied Hungary on March 19, 1944. In April 1944, Hungarian authorities ordered Hungarian Jews living outside Budapest (roughly 500,000) to concentrate in enclosed ghettos located in certain cities, usually regional government seats. Hungarian gendarmes were sent into the rural regions to round up Jews and dispatch them to the cities. None of these ghettos existed for more than a few weeks, and many were liquidated within days.
In mid-May 1944, the Hungarian authorities, in coordination with the German Security Police, began systematically to deport Hungarian Jews. SS Colonel Adolf Eichmann was chief of the team of "deportation experts" that worked with the Hungarian authorities. The Hungarian police carried out the roundups and forced the Jews onto deportation trains.
In less than two months, nearly 440,000 Jews were deported from Hungary in more than 145 trains. Most were deported to Auschwitz. Thousands were also sent to the border with Austria to dig fortification trenches.
In light of the worsening military situation and facing threats from Allied leaders of war crimes trials, the Hungarian Regent, Admiral Miklos Horthy, ordered a halt to the deportations on July 7, 1944. By that time, the only Jewish community left in Hungary was that of Budapest, the capital.