I recently watched an intriguing movie about Oliver Cromwell.
Cromwell, 1970. Richard Harris and Alec Guinness
Not knowing much about him, this movie helped only a little toward more understanding. It emphasized his assertive personality in Parliament and on the battle field, and his opposition to King Charles. The history seemed rather simplistic - perhaps the nature of a 2 hour movie - in making it Charles v. Cromwell.
Vivid battle scenes give a real sense of the action. Cromwell's forces sing Psalms heading into battle. Charles has chaplains praying and reading Scripture on the field, and at his execution.
There were several instances of swearing - in a G rated movie!
For the idea of if and when and how to resist a lawful authority with arms, I would recommend Douglas Bond's Duncan trilogy instead. The movie shows Cromwell rather emotionally-driven, marching off against the king after one instance of land seizure and harsh treatment of one prisoner by his magistrate.
Cromwell himself is a mystery to me. An honorable Puritan willing to do away with monarchy a century or two before society was ready for it? C.S. Lewis viewed him very lowly, giving Cromwell's "Lord Protector" title to the evil King Miraz in Prince Caspian. He is certainly a symbol of the danger of appeals to conscience leading to anarchy. But also of the need to oppose unjust rule.