Who is martin luther and why did he speak out against the catholic church in the 1500s?

Martin Luther was a monk who lived in Germany in the early 1500's. He believed very strongly in Christianity, was a member of the Catholic Church. Luther devoted his life to his religion. He promised to never get married, to pray regularly, and to fast to show his faith in God. Luther studied the Bible and spread its teachings to others in his town.But Martin Luther was unhappy with the Catholic Church. The leaders of the church were teaching people lessons that were not found in the Bible and that Luther did not support. In 1517, Martin Luther took action to reform the church, and in doing so he would change religion forever. 

Answer is for sure Bold but concerned.