Boris III was the Tsar of Bulgaria from 1918 until his death in 1943. He ascended to the throne after the abdication of his father, Ferdinand I, and was known for his efforts to modernize the country and maintain its independence during a turbulent period in Europe. During his reign, Boris III navigated complex political landscapes, including alliances with Nazi Germany and attempts to preserve Bulgaria's sovereignty. His rule ended abruptly when he died under mysterious circumstances, leading to significant political changes in Bulgaria and the eventual establishment of a communist regime.