Please answer the following question: Given the following passage  "Monastic reform inspired change in the secular church. The ideals that it was based upon were brought to the papacy by Pope Leo IX (pope 1049–1054), and provided the ideology of the clerical independence that led to the Investiture Controversy in the late 11th century. This involved Pope Gregory VII (pope 1073–85) and Emperor Henry IV, who initially clashed over episcopal appointments, a dispute that turned into a battle over the ideas of investiture, clerical marriage, and simony. The emperor saw the protection of the Church as one of his responsibilities as well as wanting to preserve the right to appoint his own choices as bishops within his lands, but the papacy insisted on the Church's independence from secular lords. These issues remained unresolved after the compromise of 1122 known as the Concordat of Worms. The dispute represents a significant stage in the creation of a papal monarchy separate from and equal to lay authorities. It also had the permanent consequence of empowering German princes at the expense of the German emperors.",  answer the following question. Note that the answer is present within the text.  Question: What did Gregory VII and Henry IV start?
A:
initially clashed over episcopal appointments