Boris rose to power following his father's abdication on 3 October 1918, at the end of World War I. Bulgaria was then in desperate straits. The 1919 Treaty of Neuilly involved loss of territory and the payment of reparations. As a consequence of his country's many problems, Boris experienced an exceptionally stormy reign. The 1920s were filled with internal political strife, and economic problems forced Bulgaria to depend on Germany for supplies.
Boris favored a neutralist course for his country. He proved to be an adept diplomat and an intelligent yet cautious leader who was genuinely respected by his people for his skillful handling of the many problems besetting the kingdom. He was an unwilling junior partner in the Axis alliance during World War II. Pressured into joining the alliance by Germany, Boris regained the southern Dobruja region from Romania in 1940, which led to his being known as the "King Unifier" and the "Liberator Tsar."
By 1941, Boris had little choice but to commit to the Axis powers and allow German troops to cross through his country en route to the Soviet Union. Unlike the other Balkan states, Bulgaria remained autonomous during the war. Although it did not invade Yugoslavia or Greece, its troops did garrison parts of Macedonia and western Thrace. In December, Bulgaria declared war on the United States and Britain, but Boris infuriated Adolf Hitler by withholding Bulgarian troops from the war effort and refusing to declare war on the Soviet Union or send Bulgarian Jews to the death camps. His actions helped save 50,000 Jews. Boris and Giovanna also arranged for transit visas permitting thousands of other Jews to go to Palestine.
Boris's continuous obduracy regarding German policies led to a stormy meeting with Hitler at the latter's Wolfsschanze headquarters near Rastenburg on 14 August 1943, in which Boris bluntly said that Bulgaria would follow its own path. He returned to Sofia depressed over the probable eventual fate of his country. Boris died at the royal palace in Sofia two weeks later, on 28 August 1943, most likley from an embolism, although there were suspicions he had been poisoned. A regency then took power on behalf of the underage King Simeon II, who reigned until he was deposed on 9 September 1946.
Crampton, R. J. A Concise History of Bulgaria. Cambridge: Cambridge University Press, 1997.; Groueff, Stephan. Crown of Thorns: The Reign of King Boris III of Bulgaria, 1918–1943. Lanham, MD: Madison Books, 1987.; Lalkov, Milcho. Rulers of Bulgaria. Sofia: Kibea Publishing, 1997.