World War I was a global war because countries and colonies from around the world were involved in it. It was mainly a European war, but the European countries had empires, which helped make it a global war. The Ottoman Empire’s involvement brought the war to the Middle East. In addition, there were other countries that got into the war because they felt that doing so would benefit them. Not every country in the world was involved in the war, but countries around the world were.
Britain, France, and Germany all had worldwide empires. The British Empire included South Africa, New Zealand, Canada, India, and Australia, all of which sent troops. The French and Germans had colonies in Africa. There was a little fighting there and the Europeans took men from those colonies to Europe to help in the war effort. These empires helped make WWI a global war.
The Ottoman Empire’s involvement in the war helped make it a global conflict. The Ottoman Empire controlled all of the Middle East at that time. Britain, in particular, tried to foment uprisings among the Arabs against the Ottomans. This meant that there was fighting in the Middle East.
Finally, other countries around the world decided that it was in their interests to fight. The United States joined the war rather late. China and Japan were officially involved, though their involvement was relatively minimal. The same was true of Brazil.
In these ways, we can see that countries from Africa, East Asia, Southwest Asia, and the Americas were involved in this war along with the main combatants in Europe. For this reason, we can say that WWI was a global war.