Oliver Cromwell was a member of the Parliamentarian army during the English Civil War. He rose through the ranks and eventually became the commander of the army. He led the Parliamentarian army to victory at the Battle of Marston Moor in 1644, which was a turning point in the war. He also played a key role in the Battle of Naseby in 1645, which resulted in the defeat of the Royalist army and the end of the war.
Cromwell's military victories made him a national hero and he became a symbol of the Parliamentarian cause. He was also a skilled politician and he played a key role in the negotiations between Parliament and the King. After the war, he became the Lord Protector of England and ruled the country for five years until his death in 1658.
Cromwell's legacy is complex and controversial. He is often praised for his military leadership and his role in the English Revolution, but he is also criticized for his authoritarianism and his religious intolerance. However, there is no doubt that he was one of the most influential figures in English history.