The conflict between Charles I and Parliament began as a result of a power struggle between the king and his opponents over the issue of taxation and the extent of the king's power. Charles I believed in the divine right of kings, which held that monarchs were appointed by God and therefore had absolute authority over their subjects. However, many members of Parliament believed that the power of the king should be limited by the rights of the people.

The English Civil War broke out in 1642 after years of political and religious tension between King Charles I and Parliament. Charles I believed in the divine right of kings, which gave him absolute power, while many members of Parliament wanted to limit his power and protect their own rights.

At the beginning of the war, Charles's forces, known as the Royalists or Cavaliers, had some initial successes, including victories at the battles of Edgehill and Brentford. However, the Parliamentarian forces, led by Oliver Cromwell, were ultimately able to gain the upper hand.

In 1646, after a series of battles and skirmishes, Charles I found himself in a difficult position. He had lost much of his military strength and was facing financial difficulties. He decided to surrender to the Scottish army, which had been fighting on his side but was now negotiating a peace settlement with Parliament.

Charles believed that the Scots would be more sympathetic to his cause and would help him negotiate a peace settlement that would restore his power. However, the Scots saw him as a bargaining chip in their negotiations with Parliament and promptly turned him over to the Parliamentarians.

During his captivity, Charles I was under the watchful eye of Parliament, and they offered him several opportunities to negotiate a peace settlement. In 1647, Parliament proposed the "Heads of Proposals," a document that outlined the terms of a peace settlement that would have limited the king's power and strengthened Parliament's authority. However, Charles rejected the proposal, believing that it would diminish his authority as king.

In 1648, the Second Civil War broke out, and Charles saw an opportunity to regain his throne. He secretly negotiated with various factions, including the Scots, who were unhappy with the religious policies of the English Parliament, and the Royalists, who were loyal to the king. Charles hoped to use these factions to regain his throne, but his plans were foiled when his negotiations were discovered by Parliament.

In November 1648, the army marched on London and purged Parliament of those members who were sympathetic to the king. Known as "Pride's Purge," this action left only those members who were willing to bring Charles to trial. In January 1649, Charles was put on trial for high treason, and despite his defense, he was found guilty and sentenced to death.

Charles's refusal to compromise on the issue of his power ultimately led to his downfall. Had he been willing to accept some of Parliament's proposals, it is possible that the English Civil War could have been avoided, or at least ended sooner. However, Charles's stubbornness and belief in the divine right of kings made it impossible for him to compromise, and ultimately led to his execution.

In 1649, Charles was brought to trial before a court of judges appointed by Parliament. The trial was held in Westminster Hall and lasted for several weeks. Charles was accused of high treason, and although he defended himself eloquently, the court found him guilty and sentenced him to death.

On January 30, 1649, Charles was beheaded outside the Banqueting House in Whitehall. His execution marked the end of the English Civil War and the beginning of the Commonwealth period, during which England was ruled by Oliver Cromwell as Lord Protector.