In most cases, the necessary changes in social structure for industrialization came about violently. There has been a recurring pattern where industrialization caused war and war caused industrialization. The way that war causes industrialization is simply because the necessary tools of war are industrial products. When nations become ensnared in military engagements, they increase industrial production to meet the challenge. This is how war causes industrialization. The way that industrialization causes war is because industrialization demands certain characteristics in the social structure. If these characteristics are not in place, industrialization will force their creation. The social changes required for industrialization led to worldwide turbulence in the twentieth century, widely considered the bloodiest century in human history.