Thucydides famously wrote that wars are produced by fear, honor, and interest.
The great historian Victor Davis Hanson titled his book on World War II The Second World Wars because the conflicts that evolved into that global war began as separate wars: Japan versus China; Italy versus Ethiopia; Japan versus Soviet Russia; Soviet Russia and Germany versus Poland; Soviet Russia versus Finland; England and France versus Germany; Italy versus France; Germany versus Soviet Russia; Japan versus the United States and England; and Germany and Italy versus the United States. Similarly, in 1912 fighting broke out in the Balkans; then Austria-Hungary went to war against Serbia; Germany declared war on Russia; Russia waged war on Austria-Hungary; Germany attacked Belgium and France, and England declared war on Germany. Later, Italy and the United States joined the war. Those conflicts also evolved into a global war waged on five continents, on the high seas, and in the air.
