The Prayer Book Rebellion, Prayer Book Revolt, Prayer Book Rising, Western Rising or Western Rebellion was a popular revolt in Devon and Cornwall in 1549. In that year, the Book of Common Prayer, presenting the theology of the English Reformation, was introduced. The change was widely unpopular – particularly in areas of still firmly Catholic religious loyalty (even after the Act of Supremacy in 1534) such as Lancashire.^{[citation needed]} Along with poor economic conditions, the attack on the Catholic Church led to an explosion of anger in Devon and Cornwall, initiating an uprising. In response, Edward Seymour, 1st Duke of Somerset, sent Lord John Russell with an army composed partly of German and Italian mercenaries to suppress the revolt.