Hitler transferred his headquarters to the Führerbunker ("Leader's bunker") in Berlin on 16 January 1945, where he (along with Bormann, his secretary Else Krüger, and others) remained until the end of April. The Führerbunker was located under the Reich Chancellery garden in the government district of the city centre. The Battle of Berlin, the final major Soviet offensive of the war, began on 16 April 1945. By 19 April the Red Army started to encircle the city. On 20 April, his 56th birthday, Hitler made his last trip to the surface. In the ruined garden of the Reich Chancellery, he awarded Iron Crosses to boy soldiers of the Hitler Youth. That afternoon, Berlin was bombarded by Soviet artillery for the first time. On 23 April, Albert Bormann left the bunker complex and flew to the Obersalzberg. He and several others had been ordered by Hitler to leave Berlin.
The trial got underway on 20 November 1945. Lacking evidence confirming Bormann's death, the International Military Tribunal tried him in absentia, as permitted under article 12 of their charter. He was charged with three counts: conspiracy to wage a war of aggression, war crimes, and crimes against humanity. His prosecution was assigned to Lieutenant Thomas F. Lambert Jr. and his defence to Friedrich Bergold. The prosecution stated that Bormann participated in planning and co-signed virtually all of the antisemitic legislation put forward by the regime. Bergold unsuccessfully proposed that the court could not convict Bormann because he was already dead. Due to the shadowy nature of Bormann's activities, Bergold was unable to refute the prosecution's assertions as to the extent of his involvement in decision making. Bormann was convicted of war crimes and crimes against humanity and acquitted of conspiracy to wage a war of aggression. On 15 October 1946 he was sentenced to death by hanging, with the provision that if he were later found alive, any new facts brought to light at that time could be taken into consideration to reduce the sentence or overturn it.
Gerda Bormann and the children fled Obersalzberg for Italy on 25 April 1945 after an Allied air attack. She died of cancer on 23 March 1946, in Merano, Italy. Bormann's children survived the war, and were cared for in foster homes. His eldest son, Martin, was ordained a Roman Catholic priest and worked in Africa as a missionary. He later left the priesthood and married.