The impact of World War I was as great on the Muslim world as it was on Europe and the United States. All across the world, imperial subjects were shocked and angered that their contributions to the Allied war effort were ignored. As a result, nationalist movements gained huge followings. Most of these were secular in nature, but new religious movements also appeared. Some, like the Muslim Brothers in Egypt and Muhammadiya in Indonesia, were enormous. What is striking about the most influential religious movements of the period is that they were led by men and women who had no formal religious education. The Sunni reform movement that began in the eighteenth century had resulted in a widespread acceptance of lay leadership in religious affairs.