Ultimately, the English Civil war between 1642 and 1651 stemmed from a clash between what the monarch held to be his power versus the power of parliament. King James I was the first to instigate a clash between the monarchy and Parliament. James I was an devout believer in a doctrine known as the "divine right of kings." The doctrine held that monarchs were chosen by God and given authority by God and, therefore, no king's actions or decisions could ever be believed to be wrong. Historians trace the doctrine back to the medieval doctrine that God gives absolute power to the Church, which also ties to the belief in the infallibility of the pope. As a devout believer in the doctrine, James I believed that Parliament should do his bidding and not dispute his decisions.
James' doctrine especially caused a clash with Parliament over money. Only Parliament held the authority to collect custom duties, which are taxes levied on certain goods, transactions, and estates rather than on people, unlike the income tax. Since only Parliament had the authority to collect it, James was without one source of income; therefore, he withdrew Parliament's power and forbade the members to meet for what amounted to 10 years. Needless to say, Parliament became furious with James because they actually believed they had the authority to rule the country rather than the king.
James's son, King Charles I inherited the tension between the monarch and Parliament. What's more, he believed even more tenaciously than his father in the doctrine of the "divine rights of kings," leading to even more clashes between the king and Parliament. In fact, Charles I locked the doors of Westminster, forbidding Parliament to meet for 11 years rather than 10. Plus, he instigated more clashes with Parliament over money. He used conniving means to obtain income without Parliament, such as issuing heavy fines to any noble or genteel person tried in the Court of Star Chamber, a court reserved for important people who would not have been convicted in regular courts, and even attempting to hold the entire country responsible for paying Ship Money, a tax only paid by coastal towns to fund and ensure the protection the navy offered. The problem with King Charles levying such a tax was that only Parliament had the authority to levy taxes.
But the greatest point leading to the civil war was when Charles even angered the Scots, having become King of Scotland in 1633, by demanding they use a different prayer book in their services, leading to Scotland invading England. Since Charles needed money to fight the Scots, he had to turn to Parliament, opening the doors for Parliament to make demands of the king, such as abolishing the Court of Star Chamber. When Parliament started making demands of him, Charles marched into Westminster with 300 soldiers to have several Members of Parliament arrested. Charles's attempt at arrests made Parliament and the people Parliament represented feel particularly unsafe. Six days after the attempted arrests, a civil war broke out between King Charles and his supporters and Parliament, the Scots, and the people.