What were the 3 major themes or issues that had the most impact on World History
The three largest issues to impact world history were World War I, The Great (Global) Depression, and World War II. ... Militarism is the second cause after the nationalism one should be familiar with the situation of the world in the beginning of the century, which was the result of both industrial and democratic revolutions. Britain at that time was the largest empire in the world, and it also had the largest navy. ... Imperialism and the system of alliances are the last two major causes of the War. ... The Great Depression was the 2nd world changing event and it had profound political implications. ... In countries such as the United States and Britain, government intervention ultimately resulted in the creation of welfare systems and the managed economies of the period following the Second World War. World War II was the 3rd most important event to take place from 1900-1945 and easily had the most impact on the world.