What caused an arms race in Europe?

Arms Control Efforts Fail Moreover, Germany violated the Treaty of Versailles and began to rearm. This started a new arms race in Europe between Germany, France and Britain, and in the Pacific between Japan and the United States

Countries such as Germany and Britain engaged in a race to produce the most powerful armies through invention and mass production of weapons. This arms race is often cited as a leading cause for World War I. In the decades leading up to World War I, many European countries began to place more focus on their military might.