The real causes that led to WW1 included politics, secret alliances, imperialism and national pride. Nevertheless, there was one single event, the assassination of Archduke Ferdinand of Austria , which started a chain of events leading to war.
As regards Imperialism, some European countries like France and Britain had created large worldwide empires and had become very rich. Countries like Russia and Germany wanted to create their own empires, this caused competition and conflict between many other countries.
As regards Alliances and politics, in the years leading up to the war, the nations of Europe were constantly jockeying for power and making alliances. Germany made an alliance with Austria-Hungary and Italy in 1881. These countries all agreed to protect each other when they were attacked by France. However, Italy then made a secret alliance with France saying they would not aid Germany.
In 1914, the Archduke Franz Ferdinand , heir to the throne of Austria-Hungary was assassinated in Sarajevo. It was believed that the assassination was arranged by the Serbian government.
Then Austria-Hungary declared war on Serbia in July.
Russia began to mobilize its troops and prepare for war. In response, Germany , Austria-Hungary's close ally, declared war on Russia. A few days later, Germany declared war on France and invaded Belgium. Britain declared war on Germany and then World War I begun.
WORLD WAR II
World War II was a direct result of the turmoil left behind by WW1. Here are some events that led to WW2:
-Treaty of Versailles: This Treaty ended WW1 between Germany and the Allied Powers. Germany was forced to "accept the responsibility" of the war damages suffered by the Allies. The treaty required that Germany paid a huge sum of money called "reparations". At that time, Germany's economy was in ruins, there were people starving and the government was a chaos.
-Japanese expansion: before WW2, Japan was growing rapidly. However, as an island nation, they did not have the land or the natural resources to sustain their growth. They began to look to grow their empire in order to gain new resources so they invaded Manchuria in 1931 and China in 1937.
-Fascisim: With the economic problems left behind by WW1, some countries were taken over by dictators who formed powerful fascist governments. Their first fascist government was Italy which was ruled by the dictator Mussolini. Italy invaded and took over Ethiopia in 1935. Hitler would later emulate Mussolini in his takeover of Germany. Spain was also under dictatorship, ruled by Franco.
- The Nazi Party: The Germans were desperate for someone to turn around their economy and restore their national pride. Hitler offered them hope. In 1934, Hitler was proclaimed the "Fuhrer" , the dictator of Germany.
He resented the restrictions put on Germany by the Treaty of Versailles. He rearmed Germany, allied Germany with Italy . He wanted to expand his empire , he first took over Austria in 1938 and that was when WW2 begun.