original_query: What were the key roles of Robert Devereux, 3rd Earl of Essex, during the 17th century?
query: What were the key roles of Robert Devereux, 3rd Earl of Essex, during the 17th century?
answer: Robert Devereux, 3rd Earl of Essex, served as a Parliamentarian soldier and leader during the English Civil War, initially as Captain-General and Chief Commander of the Parliamentarian army.  He also had a military career prior to the Civil War, serving in continental armies and in the King's army during the Bishops' Wars.  He played a significant political role as a member of the House of Lords, opposing the Stuart monarchy and participating in key political events leading up to the war.  His involvement with the Peace Party and his eventual resignation as Captain-General marked a turning point in the war.