Why did the League of Nations fail? (Choose all that apply.)

a. The Soviet Union did not join, so the League of Nations never achieved a preponderance of power.
b. The League of Nations failed to provide credible military commitments to defend all members.
c. The principle of unanimity was undercut by the fact that all states had veto power, so the aggressor state could veto any resolution.
d. The Covenant of the League of Nations was based on the agreement reached at the Congress of Vienna after the Napoleonic Wars that decentralized military power.

b. The League of Nations failed to provide credible military commitments to defend all members.
c. The principle of unanimity was undercut by the fact that all states had veto power, so the aggressor state could veto any resolution.