During World War II, the Kingdom of Hungary was a member of the Axis powers.^[74] In the 1930s, the Kingdom of Hungary relied on increased trade with Fascist Italy and Nazi Germany to pull itself out of the Great Depression. Hungarian politics and foreign policy had become more stridently nationalistic by 1938, and Hungary adopted an irredentist policy similar to Germany's, attempting to incorporate ethnic Hungarian areas in neighboring countries into Hungary. Hungary benefited territorially from its relationship with the Axis. Settlements were negotiated regarding territorial disputes with the Czechoslovak Republic, the Slovak Republic, and the Kingdom of Romania. On November 20, 1940, Hungary became the fourth member to join the Axis powers when it signed the Tripartite Pact.^[75] The following year, Hungarian forces participated in the invasion of Yugoslavia and the invasion of the Soviet Union. Their participation was noted by German observers for its particular cruelty, with occupied peoples subjected to arbitrary violence. Hungarian volunteers were sometimes referred to as engaging in "murder tourism."^[76]

After two years of war against the Soviet Union, Prime Minister Miklós Kállay began peace negotiations with the United States and the United Kingdom in autumn of 1943.^[77] Berlin was already suspicious of the Kállay government, and in September 1943, the German General Staff prepared a project to invade and occupy Hungary. In March 1944, German forces occupied Hungary. When Soviet forces began threatening Hungary, an armistice was signed between Hungary and the USSR by Regent Miklós Horthy. Soon afterward, Horthy's son was kidnapped by German commandos and Horthy was forced to revoke the armistice. The Regent was then deposed from power, while Hungarian fascist leader Ferenc Szálasi established a new government, with German backing. In 1945, Hungarian and German forces in Hungary were defeated by advancing Soviet armies.^[78]

Approximately 300,000 Hungarian soldiers and more than 600,000 civilians died during World War II, including between 450,000 and 606,000 Jews^[79] and 28,000 Roma.^[80] Many cities were damaged, most notably the capital Budapest. Most Jews in Hungary were protected from deportation to German extermination camps for the first few years of the war, although they were subject to a prolonged period of oppression by anti-Jewish laws that imposed limits on their participation in public and economic life.^[81]