How did alliances between European countries cause a conflict between 2 countries to become a world war?

Alliances between European countries created a web of obligations that drew multiple nations into conflict. When tensions escalated between two countries, such as Austria-Hungary and Serbia in 1914, their respective allies—like Germany, Russia, and France—were bound to support them due to these agreements. This interconnectedness transformed a localized dispute into a larger confrontation, leading to World War I as nations mobilized in defense of their allies, ultimately escalating the conflict into a global war.