The New Model Army delivered a decisive blow to the Royalist forces in the Battle of Naseby on June 14, 1645. This battle, which took place in Northamptonshire, was one of the most significant engagements of the English Civil War. The Royalist army, commanded by King Charles I and his generals, was outmaneuvered and overwhelmed by the highly disciplined and well-organized New Model Army, led by Sir Thomas Fairfax and Oliver Cromwell. The crushing defeat effectively marked the beginning of the end for the Royalist cause.

Following their devastating loss at Naseby, the Royalist forces suffered a series of further defeats, and King Charles I was left with no viable military support. By 1646, realizing his position was untenable, Charles surrendered not to Parliament, but to the Scottish forces, hoping to negotiate better terms. However, the Scots, after months of deliberation, handed Charles over to the English Parliament in exchange for a payment of £400,000, effectively sealing his fate.

Despite the king’s surrender, tensions soon emerged within the victorious Puritan factions regarding what should be done with him. The Presbyterians, who made up a large portion of Parliament, wanted to retain Charles as a figurehead monarch under a constitutional system, hoping for a settlement that would preserve some form of traditional rule. On the other hand, the more radical Independents, led by Cromwell and the Army, viewed Charles as a traitor who could not be trusted. They advocated for his trial and execution, believing that England should become a republic, free from monarchy altogether.

As these factions struggled to agree, negotiations with the king failed. Charles, believing that his opponents were too divided to act decisively against him, attempted to manipulate the situation to his advantage. In 1647, he escaped captivity and allied himself with the Scots, convincing them to support his cause in what became known as the Second English Civil War.

This betrayal shattered any remaining hopes of reconciliation. The New Model Army, under Cromwell’s leadership, swiftly crushed the Royalist uprisings in 1648, solidifying its dominance. By this point, many in the army and radical Puritan groups saw Charles as an obstacle to peace. In January 1649, Charles I was put on trial for treason, found guilty, and executed on January 30, 1649—a shocking event that marked the first time an English king was legally put to death by his own subjects.

With the monarchy abolished, England was declared a Commonwealth (or republic), governed by Parliament and the army, with Cromwell emerging as its most powerful leader. However, deep divisions remained within the Puritan movement, and the struggle for control over England’s future was far from over.