The two World Wars were the most destructive conflicts of modern European history. Although they occurred in different circumstances, both wars were rooted in the political, economic and military tensions that developed in Europe during the late nineteenth and early twentieth centuries. The First World War broke out in 1914, while the Second World War began in 1939. Several major factors contributed to their outbreak. The First World War was largely the result of the growth of aggressive nationalism, imperialist rivalry, militarism and the alliance system. Nationalism encouraged European nations to seek greater political power and prestige. In the Balkans, nationalist movements among Serbs and other Slavic peoples challenged the Austro-Hungarian Empire. At the same time, France sought revenge against Germany for the loss of Alsace-Lorraine in the Franco-Prussian War. Imperialism intensified competition among European powers. Britain, France, Germany and other states competed for colonies, markets and strategic influence in Africa and Asia. Germany's late entry into imperial