Assuming you mean the world wars, this is what happened.
World War 1- A figure of royalty, Franz Ferdinand was shot by a member of a terrorist group, Austra-Hungary Declares War on serbia, which both countries brough their allies in it as well. For 4 years, brutal combat took place mostly in Europe and Eastern Europe. The Allies won, Treaty of Versailles was established, which punished Germany. The war was from 1914-1918
World war 2- Adolf Hitler took over a weakened Germany, which Hitler blamed all of Germany's problems on Jewish people. Anti-Semitic laws were passed, then the genocides started to happen after the invasion of Poland. The Nazis took over many countries in Europe, including France. Then in 1941, the Japanese bombed Pearl Harbor, which brought the US in the fight. The war lasted from 1939-1945 and claimed many lives. Germany surrendered, then Japan after the US dropped two atomic bombs on Japan.
This is a very crude description of each war, but I hope this helped.
