The most striking case for rescue comes from Hungary. Holocaust-era Hungarian governments, under the dictator Miklos Horthy, oscillated between sincere and reluctant collaboration with the Germans, depending on the balance of forces in the larger war and the room for maneuver under German pressure. Between 1938 and 1941, Hungary passed laws modeled on the German Nuremberg laws; supported Germany’s pre-war grabs for territory; and, in June 1941, joined the war against Russia.
All the same, from March 1942 to March 1944, the government stalled anti-Semitic measures as much as it judged possible. When, in September 1942, the Germans begin pressing Hungarians on deportations, they discovered that a screen of extremists covered a government determined not to deport the Jews.
By March 1944, the SS had become fed up with the Hungarians and tantalized by the huge pool of Jews who have remained safe all through the war in the heart of Nazi Europe. The Germans forced Horthy to replace his prime minister, and German officials came to Budapest to direct the annihilation of the Hungarian Jews. Under German direction the Hungarians completed the exclusion of Jews from the economy, Jews were required to wear the star, travel restrictions were imposed, and telephones were confiscated.
Between April and July 1944, the Jews were “concentrated.” Deportations began in April, but most took place between May and July 1944. By 9 July 1944 437,000 Jews had been deported to Auschwitz where ninety percent of them were killed upon arrival. On 6 July 1944, Horthy ordered deportations stopped; on 25 August 1944, Horthy got rid of the pro-German cabinet. In mid-October 1944, the Germans overthrew the Hungarian government and installed a puppet regime. Over the next month, the Germans deported another 65,000 Jews. Then the Hungarian fascists ran wild for a couple of months, leaving 10,000 to 20,000 more Jews dead. The Red Army captured Budapest on 13 February 1945.
What could have been done to prevent this last great slaughter? First, the Hungarian Jews could have been allowed to emigrate to Britain, Palestine, and the United States before the war ever began. This didn’t happen because the United States had sharply restricted immigration from Southern and Eastern Europe in 1924; and Jewish immigration to Palestine had brought a violent Arab opposition in the 1930s.
Second, the Hungarian Jews could have been moved to a place of greater safety before the Germans got control of Hungary in March 1944. Essentially, that meant through Rumania to the Black Sea to … where? Palestine? Would Hungarian Jews willingly have placed themselves within reach of the Rumanians or the Germans?
Third, the deportations could have been prevented in some fashion by military action. Essentially, this comes down to bombing the railroad lines to Auschwitz. This might have slowed up the process. At the same time, the Germans had a lot of experience repairing bombed railroad lines and bridges. At the end of the war, they also used “death marches.”
Fourth, the gas chambers at Auschwitz could have been destroyed before all or most or some of the Hungarian Jews arrived. The British and American air forces didn’t want to divert assets from purely military operations. The national leaderships didn’t want to force them.
 See: Struma disaster – Wikipedia Not reaching for excuses here; just trying to imagine real discussions.
 See: Auschwitz bombing debate – Wikipedia Nor did Jewish organizations.