The Parliamentary army refers to the military forces that supported the Parliament during the English Civil War (1642-1651). This army was primarily composed of soldiers who opposed the rule of King Charles I and sought to establish a government based on parliamentary authority. Led by notable figures such as Oliver Cromwell, the Parliamentary army played a crucial role in several key battles, including the Battle of Naseby. Their victory ultimately led to the defeat of the Royalists and the establishment of a republican government in England, marking a significant shift in the country's political landscape.