The First World War affected colonies around the world in several ways.

First, the acquisition of colonies was one of the causes of the war. Germany had watched as Great Britain and France snatched up most of the best colonial regions—India, Egypt, Nigeria, and South Africa for the Brits; Morocco, Algeria, and much of West Africa for the French. Germany coveted colonies of its own but had to settle for German East Africa (now Tanzania), German West Africa (Namibia), Togoland (Togo), and Cameroon. The Germans believed that winning WWI would allow it to seize colonies from the Allied Powers.

Second, colonies provided many resources for the war effort. Not only were raw materials such as oil, rubber, tin, and other minerals drawn from overseas colonies, but millions of colonial troops joined their colonial masters in the trenches. With the conflict devolving into a war of attrition, troops from British and French colonies supplemented the men supplied from the home countries. Without those millions of soldiers coming from their colonies, it's possible Britain and France may not have been able to maintain sufficient troop strength to create the stalemate that marked much of the war.

Third, the minor skirmishes throughout the colonies provided some interesting sidelights to the trench warfare on the Western Front. German colonial troops in East Africa tied up more than 125,000 Allied forces who otherwise could have served in the trenches. Lawrence of Arabia led a British effort to tie down Ottoman Empire forces in the Middle East, again keeping those troops from joining the Central Powers along the Western and Eastern fronts.

Finally, the aftermath of colonial involvement in World War I can be seen today. The betrayal of the Arab forces who had allied with the Brits under the promise of independence and self-determination led to a deep mistrust of the West that informs some of the issues plaguing the Middle East to this day. The Balfour Declaration in 1917, expressing Britain's support for a Jewish homeland in Palestine, led to the eventual creation of Israel 30 years later. Germany's African colonies transferred to British and French control. The British Empire was at its peak, but the seeds of its destruction also were sown during WWI. The Brits had promised colonies more local control in order to secure the participation of colonial troops in the war effort, then quickly reneged on those promises once the war ended. India, the crown jewel of the Empire, took the broken promises very hard, and soon after the war ended, Indians chafing under colonial rule began rebelling against the Brits, leading—nearly 30 years later—to independence.