Germany gained importance as the Holy Roman Empire of the German Nation, which was the first Reich (this word means empire). It was started by Charlemagne who became the first Holy Roman Emperor in 800 AD, and it lasted until 1806, the time of the Napoleonic Wars.
The Second Reich was started with a treaty in 1871 in Versailles. The biggest state in the new German Empire was Prussia. The rulers were called Kaisers or "German Emperors", but they did not call themselves "Emperors of Germany". There were many smaller states in the Empire, but not Austria. Germany stayed an empire for 50 years.
In 1866 Prussia won the war against Austria and their allies. During this time Prussia founded the North German Confederation. The treaty of unification of Germany was made after Germany won the Franco-Prussian War with France in 1871. In World War I, Germany joined Austria-Hungary, and again declared war on France. The war became slow in the west and became trench warfare. Many men were killed on both sides without winning or losing. In the Eastern Front the soldiers fought with the Russian Empire and won there after the Russians gave up. The war ended in 1918 because the Germans could not win in the west and gave up. Germany's emperor also had to give up his power. France took Alsace from Germany and Poland got the Danzig corridor. After a revolution, the Second Reich ended, and the democratic Weimar Republic began.
After the war, there were a lot of problems with money in Germany because of the Peace Treaty of Versailles, which made Germany pay for the costs of World War I and the worldwide Great Depression.
The Third Reich was Nazi Germany; it lasted 12 years, from 1933 to 1945. It started after Adolf Hitler became the head of government. On 23 March 1933, the Reichstag (parliament) passed the Enabling Act, which let Hitler's government command the country without help from the Reichstag and the presidency. This gave him total control of the country and the government. Hitler, in effect, became a dictator.
Hitler wanted to unify all Germans in one state and did this by taking over places where Germans lived, such as Austria and Czechoslovakia; Hitler also wanted the land in Poland that Germany had owned before 1918, but Poland refused to give it to him. He then invaded Poland. This started World War II on 1 September 1939. In the beginning of the war, Germany was winning and even successfully invaded France. It managed to take over much of Europe. However, Germany attacked the Soviet Union in 1941 and after the Battle of Kursk, the German Eastern Front began a slow retreat until war's end. On 8 May 1945, Germany gave up after Berlin was captured, Hitler had killed himself a week earlier. Because of the war, Germany lost a lot of German land east of the Oder-Neiße line, and for 45 years, Germany was split into West Germany and East Germany. Other events happened during the war in Nazi Germany, including the Holocaust, the mass genocide of Jews and other peoples, for which some Nazis were punished in the Nuremberg Trials.
In 1989 there was a process of reforms in East Germany, which lead to the opening of the Berlin Wall and to the end of socialist rule in Germany. These events are known as the Wende or the Friedliche Revolution (Peaceful Revolution) in Germany. After that, East Germany joined West Germany in 1990. The new Germany is a part of the European Union.