In early 1943, Nazi officials requested that Bulgaria deport its Jewish population to German occupied Poland. The request caused a public outcry, and a campaign whose most prominent leaders were Parliament Vice-Chairman Dimitar Peshev and the head of the Bulgarian Orthodox Church, Archbishop Stefan, was organized…. Boris refused to permit the extradition of Bulgaria's 50,000 Jews…. The Bulgarian government utilized Swiss diplomatic channels to inquire whether possible deportations of the Jews can happen to British-controlled Palestine by ships rather than to concentration camps in Poland by trains…. However, this attempt was blocked by the British Foreign Minister, Anthony Eden. Eventually, Boris did succumb to the German demand for the extradition of 11,343 Jews from those territories re-occupied by Bulgaria, but the extradition of the Jews from pre-war Bulgaria was stopped.
These two decisions have led to a position today where a large number of people regard Boris as a hero for saving Bulgaria's Jews, and a large number criticize him for condemning those from the occupied new territories…. Bulgaria paid for the transport to Treblinka….
Most irritating for Hitler, however, was the Tsar's refusal to declare war on the Soviet Union or send Bulgarian troops to the Eastern front. On 9 August 1943, Hitler summoned Boris to a stormy meeting at Rastenburg, East Prussia, where Tsar Boris arrived by plane from Vrazhdebna on Saturday, 14 August. While Bulgaria had declared a 'symbolic' war on the distant United Kingdom and the United States, at that meeting Boris once again refused to get involved in the war against the Soviet Union, giving two major reasons for his unwillingness to send troops to Russia — first, that many ordinary Bulgarians had strong Russophile sentiments; and second, that the political and military position of Turkey remained unclear. The 'symbolic' war against the Western Allies, however, turned into a disaster for the citizens of Sofia as the city was heavily bombarded by the US and the British Royal Air Force in 1943 and 1944….
Shortly after returning to Sofia from a meeting with Hitler, Boris died of apparent heart failure on 28 August 1943. Conspiracy theories instantly sprang up, many choosing to believe that he was poisoned by Hitler in an attempt to put a more obedient government in place. The evening before the illness occurred, Boris had an official dinner in the Italian embassy. The question has never been settled and many people remain of the belief that Boris was murdered, in spite of no evidence being available. According to the diary of the German attache in Sofia at the time, Colonel von Schoenebeck, the two German doctors who attended the king – Sajitz and Hans Eppinger – both believed that the king had died from the same poison that Dr. Eppinger had allegedly found two years earlier in the postmortem examination of the Greek prime minister Ioannis Metaxas, a slow poison which takes weeks to do its work, and which causes the appearance of blotches on the skin of its victim before death…. Boris was succeeded by his six-year-old son Simeon II under a Regency Council headed by Boris's brother, Prince Kyril of Bulgaria.