World War I and World War II were the last declared wars fought in Europe and Asia.
World War I was a global war initiating in Europe that protracted from 28 July 1914 to 11 November 1918. It was considered as "the war to end all wars."
World War II also known as the Second World War, was a global conflict that lasted from 1939 to 1945. The vast majority of the world's countries, even all the great powers, eventually created two opposing military alliances: the Allies and the Axis.