English Civil War: Battle of Naseby: Twelve thousand Royalist forces are beaten by fifteen thousand Parliamentarian soldiers.

The English Civil War or Great Rebellion was a series of civil wars and political machinations between Royalists and Parliamentarians in the Kingdom of England from 1642 to 1651. Part of the wider 1639 to 1653 Wars of the Three Kingdoms, the struggle consisted of the First English Civil War and the Second English Civil War. The Anglo-Scottish War of 1650 to 1652 is sometimes referred to as the Third English Civil War.

The Battle of Naseby took place on 14 June 1645 during the First English Civil War, near the village of Naseby in Northamptonshire. The Parliamentarian New Model Army, commanded by Sir Thomas Fairfax and Oliver Cromwell, destroyed the main Royalist army under Charles I and Prince Rupert. The defeat ended any real hope of Royalist victory, although Charles did not finally surrender until May 1646.

Roundheads were the supporters of the Parliament of England during the English Civil War (1642–1651). Also known as Parliamentarians, they fought against King Charles I of England and his supporters, known as the Cavaliers or Royalists, who claimed rule by absolute monarchy and the principle of the divine right of kings. The goal of the Roundheads was to give to Parliament the supreme control over executive administration of England.

The Long Parliament was an English Parliament which lasted from 1640 until 1660, making it the longest-lasting Parliament in English and British history. It followed the fiasco of the Short Parliament, which had convened for only three weeks during the spring of 1640 after an 11-year parliamentary absence. In September 1640, King Charles I issued writs summoning a parliament to convene on 3 November 1640. He intended it to pass financial bills, a step made necessary by the costs of the Bishops' Wars against Scotland. The Long Parliament received its name from the fact that, by Act of Parliament, it stipulated it could be dissolved only with agreement of the members; and those members did not agree to its dissolution until 16 March 1660, after the English Civil War and near the close of the Interregnum.