What was a major reason for the failure of disarmament in the early 20th century?

The major reason for the failure of disarmament in the early 20th century was the widespread fear among nations of becoming vulnerable if they disarmed first. This apprehension was rooted in a fragile geopolitical landscape characterized by rising nationalism, imperial competition, and a growing arms race among major powers. Countries were hesitant to reduce their military capabilities, fearing that doing so would leave them exposed to aggression from rivals or potential enemies.

This mindset created a cycle of distrust, where nations opted to maintain or even expand their arsenals, leading to heightened tensions and ultimately contributing to the outbreak of conflicts such as World War I. The belief that disarming could lead to a strategic disadvantage outweighed any theoretical benefits that might arise from collective disarmament agreements.