Archduke Franz Ferdinand of Austria-Hungary, was driving through Sarajevo Bosnia, with his wife. During this time their was conflict between Serbia and Austira-Hungary. Serbia wanted to be their own independent nation, and with their own qualities
So a Serbian terrorist group, known as the Black Hand, were planning to assassinate the archduke. So that their nation could gain independence, and become their own country. This way it shows the empire what they want.
The terrorist group successfully killed the archduke and his wife. Which caused Austria-Hungary to declared war on Serbia, and Russia came to aid them. Which eventually dragged France into it, along with other countries. Which led to countries making alliances to prove which army was the strongest.
The Germans had took most of the blame once the war ended. They also head to give up parts and their other type of military technology. So they couldn't even be allowed to have some of that technology. That was part of the Treaty of Versailles which the allied powers made.
A new form of combat was introduced during this time. Many people died because of new technology and gas weapons. This is known as trench warfare.
Overall Germany suffered many of the consequences for their terrible actions throughout this war.