"The Spark That Touched Off World War I/The arrest of the Bosnian student, Princip, pictured here, followed the assassination of the Archduke Francis Ferdinand of Austria at Sarajevo on June 28, 1914. The assassination was recognized by the Central Powers to be an adequate casus belli and it was followed by the presentation to Serbia of an ultimatum from Austria on July 23. Five days later Austria declared war on Serbia - and that was the beginning of World War 1."