How did the complex web of European alliances contribute to the outbreak of WW1

The Europeans alliance contribute to the outbreak of ww1 is by dividing the rival military power into two alliances.

Explanation:

That is triple alliance and triple entente. Then the six allies of Europe are Britain, France, Russia, Austria - Hungary, Italy, Germany. The first three countries joined with triple entente and other with triple alliance.

The two great alliances outbreak the war. The spark of the war due to the assassination of Franz Ferdinand in Sarajevo on June 1914. Most alliances would agree to protect one another if either country in that alliance got attacked by other countries.