A long time ago, there was a big fight called World War I. It happened because many countries wanted to be the most powerful and they were fighting over land, money, and resources. The main countries that were fighting were called the Allies (which included France, Britain, and Russia) and the Central Powers (which included Germany, Austria-Hungary, and the Ottoman Empire).
The war started in 1914 and lasted for 4 years. Soldiers had to leave their families and homes to fight in the battlefields. They had to walk for miles and miles, carrying heavy weapons and wearing heavy clothes. They slept in the mud and cold, and they didn't have much food to eat. Many soldiers got sick or hurt, and some even died.
There were new inventions like tanks, airplanes, and chemical weapons that were used during the war. These new weapons made the fighting even more dangerous and many people died because of them. The war was fought on many fronts, including in Europe, Africa, and the Middle East.
Finally, in 1918, the Allies won the war. But many people died, and many countries were left in ruins. After the war, new countries were created, and some borders were changed. The war had a big impact on the world, and it led to changes in politics, economics, and society.