Who started the war in June 28 1914-1919?

The conflict that began on June 28, 1914, known as World War I, was triggered by the assassination of Archduke Franz Ferdinand of Austria-Hungary by Gavrilo Princip, a member of the nationalist group known as the Black Hand. This event set off a chain reaction of alliances and mobilizations among the major European powers. Austria-Hungary declared war on Serbia, leading to the involvement of Russia, Germany, France, and the United Kingdom, resulting in a widespread and devastating war. The underlying causes included militarism, alliances, Imperialism, and nationalism.