Why did old stone churches, a symbol of peace and God have battlements?
Firstly battlements are a medieval architectural symbol of power so as the church carried power it strove to show this in grand architecture that the populus would understand, whether they were actual or cosmetic. Another reason is that in a time when most building were wooden and the church was the only stone building it makes sense to fortify it so that the church could protect its wealth. Early churches were not fortified. The arrow slits and crenellation are on churchs built or added to during the 12th to 14th Centuries so that would also point to the fortifications being totally cosmetic (as in the first point). The suggestion that the defences (many of them unusable) were to protect against Muslims is incorrect, Durham cathedral was constructed in part by Muslim masons as they had some of the best skills in the medieval world. The Viking raids had also long been over before this style of architecture was imported by the Normans into England.
