The driving causes of the English Civil War (1644 - 1646) were religious disagreements and the idea that the king had too much power. Religion disagreements were different back then than they are now. Today, in America, if you have a religious disagreement you might lose a couple friends but the government will let you do whatever. Back then in England, however, you and your friends had to go on a campaign of angry letters and illegal speeches so you could start an army, then you charge into everyone in town who disagrees with you and cut their heads off. That's basically the idea of the English Civil War.
The faceoff was between Royalists and Parliamentarians. The Royalists were defending the king, and the Parliamentarians (or roundheads) were trying to dethrone the king because he was abusing his power. Both sides thought what they were doing was right, so both of them fought furiously for their causes for two years.
Royalist uniforms
Roundhead uniforms
In the end, the roundheads won the war. They charged into the capitol, arrested all the enemy soldiers, and, (of course) cut off the king's head. The levelers were useful in the war; they fought alongside the Roundheads because they wanted to make the king give up some of his power. The levelers believed that there is a universal right and wrong, and that no king can make it ok to do wrong or wrong to do right. The English Civil War had a lasting impact on history and promoted religious freedom and doing right.
This is really good I would mabye add one more paragraph, but otherwise it is perfect.