I've been studying about Oliver Cromwell, and I see all of his accomplishments as being "God's Will" everytime he speaks about his actions. Yet I don't see any real reason for this conviction, which as far as I can tell, was labelled a "conversion experience". How would you describe what that would have been like? Or why it was so powerful?
It's obvious he believed in God's Will when he turns down the crown to "forsake personal glory". But he sure took a lot of glory from the battlefield and used it to achieve personal and political gain, even securing a life long financial benefit from his battlefield actions.
So what was really going on with Cromwell?
Early modern people believed very profoundly and very literally in the idea of divine providence, especially as put forth by Calvin in his Institutes of the Christian Religion. In the 17th century religion was not merely something you could opt of: church attendance was required by law. With so many aspects of early modern life completely out of ordinary people's hands, it is hardly surprising that belief in providence would have made life's ills a little easier to bear.
In addition to being motivated by Parliamentary rights, Cromwell and his Roundheads were motivated by the puritan belief that Charles I was reforming his Church in a direction too far away from the Calvinist consensus reached under Elizabeth, and too close back to Roman Catholicism. In overthrowing Charles I, Cromwell and the Parliamentarians wished to either 1) reinstate the previous Calvinist status quo, or 2) institute even more puritan reforms than the Elizabethan Settlement had allowed. Not all Parliamentarians had the same motives.
Because of Original Sin, Calvinism sees mankind as inherently sinful, and therefore anything derived of mankind as inherently sinful. By claiming that something has been ordained by God's providence, people could claim that rather than men, the grace of God had made it happen. Therefore, Cromwell was claiming that Parliament's success was not due to anything he personally did, except that he did it through divine blessing - because God himself wanted to purify the English Church, undo Catholic innovations, and reinstate Calvinism.
EDIT: Alexandra Walsham's Providence in Early Modern England is a great resource if you're looking to learn more about it.
And if anyone could explain how the slaughter of the Irish made sense to his religious perspective, I'd be rather appreciative.