How did the alliance system turn the 1914 Balkan crisis into a wider war?

The alliance system transformed the 1914 Balkan crisis into a wider war by creating a "chain-reaction" effect, where regional tensions between Austria-Hungary and Serbia triggered broader obligations among the Great Powers.1

Following the assassination of Archduke Franz Ferdinand, Austria-Hungary sought to crush Serbia, relying on a "blank check" of support from Germany. This move activated the opposing alliance structures:21

• The Triple Alliance: Germany’s support for Austria-Hungary escalated the conflict, as Germany felt compelled to defend its only reliable ally and feared encirclement by the Triple Entente.231
• The Triple Entente: Russia viewed itself as the protector of the Slavic cause and Serbia. When Russia ordered general mobilization to support Serbia, it triggered German military plans, which in turn forced France to mobilize due to its own alliance with Russia.231
• The Role of Neutrality: The German invasion of neutral Belgium to reach France brought Great Britain into the war, as Britain was committed to defending Belgian neutrality.23

Ultimately, the rigid military mobilization schedules and the perceived necessity of honoring alliance commitments prevented localizing the conflict, causing the crisis to spiral into World War I.21