Respuesta :
The immediate start of WWI was the assassination of the Archduke. A Serbian gang member, Gavrilo Princip, shot the Archduke, which really angered Austria, so Austria declared war on Serbia, which eventually led to WWI. The sinking of the Lusitania happened in 1915 and the German invasion of Poland was the start of WW2.
When Franz Ferdinand was assassinated by Gavrilo Princip, Austria-Hungary declared war on Serbia, starting a chain of events which would get many countries involved in what would be called The Great War, or as we know it now, World War I