The Parliamentary Army was a military force established by the Parliament of England during the English Civil War (1642-1651). It was formed to oppose the royalist forces loyal to King Charles I. The army played a crucial role in the conflict, advocating for the authority of Parliament over the monarchy. Led by notable figures such as Oliver Cromwell, the Parliamentary Army was known for its disciplined troops and innovative tactics. Its victories, including the decisive Battle of Naseby in 1645, significantly weakened royalist power and contributed to the eventual trial and execution of King Charles I.