Final answer:
The failure of the Schlieffen Plan altered the trajectory of World War I by initiating a two-front war and involving multiple nations.
Explanation:
The failure of the Schlieffen Plan to quickly defeat France had significant implications for the course of World War I. Germany underestimated Belgian and French resistance, leading to a two-front war instead of the intended swift victory over France. This miscalculation drew Great Britain into the conflict, escalating the war on the Western Front and ultimately involving the Central Powers and the Allied Powers.
Learn more about Schlieffen Plan failure here:
https://brainly.com/question/43785573
