The simple picture of the English Civil War as a war between King and Parliament is not only simple, it's also Anglocentric and oversimplified. It is necessary to go behind King vs Parliament to understand Irish and Scottish events and modern attitudes. A broader, more inclusive, name for the wars that make up the English Civil War is "The Wars of the Three Kingdoms", with the English Civil War (or, if we prefer, the three English Civil Wars) being part of this broader conflict.

The wars actually began in Scotland, as Scottish resistance to Charles I's attempt to Anglicanise the Scottish Church. This was not just about religious freedom, but also political: should the English and Scottish Churches be unified, and what would this mean for centralisation vs decentralisation (Presbyterianism) for the Scottish church. The majority of Scotland supported an independent and Presbyterian Church of Scotland, keeping their own prayer books and Book of Discipline (the regulations of the Scottish Church). Charles wanted to unify the Church of England and the Church of Scotland, with a unified church with an Anglican model (i.e., non-Presbyterian). In addition, he wanted a uniformity of church services, and attempted to impose the Anglican Book of Common Prayer on Scotland. Further, his attempted reforms of the Churches was viewed by many as steps toward a return of Catholicism.

Scottish response was a widely-supported "National Covenant" to resist such religious innovation, and Scotland expelled the bishops (agents of the King and tools of royal control of the Church) and rejected the King's changes. Charles, not inclined toward compromise, went to war to regain control of the Scottish Church. Charles, having refused to deal with the English Parliament for a decade (again, he was not inclined toward compromise), did not summon Parliament to fund the war, and went to war with his own inadequate resources. There was little fighting (and the Covenanters generally came out as the winners in it), and the war fizzled out in Charles's lack of money.

Charles insisted on a second round, and had no source of funds other than Parliament. For the first time in a decade, he summoned Parliament. Charles was not happy with Parliament, and Parliament was not happy with Charles. Parliament insisted on outstanding grievances being addressed before they would fund his war. Charles refused to compromise, and dismissed Parliament, and again went to war with inadequate resources. Meanwhile, Charles also sought support from (Catholic) Ireland, and got it, promising concessions to Irish Catholics in return.

The Covenanters denied the Irish invasion an opportunity to land, and invaded England. Charles's army collapsed. The treaty with the Coventers required Charles to pay for the support of the Scottish army holding Newcastle, and Charles had to summon Parliament again. One thing that both Parliament and the Scots opposed the King on was his attempt to use Irish forces to impose his religious demands on Scotland - Catholic military power made his changes to the Church look even more dangerously Catholic. Parliament and Scotland made noises about invading Ireland to stop such things from happening by suppressing Irish Catholicism. Ireland rebelled, successfully getting Parliament, King, and Scotland to agree on something: a Catholic-ruled Ireland was unacceptable, and the King's rule over Ireland had to be preserved. So English armies went to Ireland, and Scottish armies, too.

Despite an agreed anti-Irish Catholic stance, the disputes between King and Parliament led to the opening of the English Civil War proper. Charles's armies in Ireland returned to England to fight Parliament, and the Irish rebels gained control of most of Ireland. Scottish troops remained to help their fellow Protestants in Ulster. The fighting in Ireland continued while the First English Civil War was fought in England. In England, 4 years of war led to Charles surrendering to the Scottish Covenanters, and Parliament and Scotland sought an acceptable compromise for long-term peace. The loose cannon was the New Model Army, unwilling to give up the political and religious rights they had fought for. The King, the loser of the previous 4 years of war, was more a pawn for these factions than an independent actor. Scotland feared the Army as a threat to Presbyterianism, and Parliament saw the Army as the wrong kind of democracy. Scotland and Charles saw their chance with each other, and Charles offered to make England Presbyterian for a minimum of three years in exchange for Scottish support. The Second English Civil War began in 1648, with Scotland and King against Parliament and Army. The fighting was over by the end of the year. The ongoing disputes between Parliament and Army erupted again after victory, leading to the Army's purge of Parliament (Pride's Purge), and the now-compliant Parliament executed Charles. The Army-dominated Council of State and the post-purge "Rump Parliament" took over England for the first years of the Commonwealth (followed by Cromwell's dismissal of Parliament and more open rule as dictator Lord Protector). Charles II became the new King of Scotland.

England ruled by the Army and Parliament was not going to coexist with Scotland ruled by Charles II, and the Third English Civil War began in 1649. Scotland lost the war and its independence (not just its King, but also its Parliament), coming under direct foreign (English) rule. Cromwell's role both the architect of the Army's victory and Scotland and foreign dictator did not endear him to the Scottish people of the time, nor to modern Scottish memory.

Similarly, Ireland had to be reconquered. The Cromwellian conquest was brutal, for example, the massacre of the defending garrison and Catholic priests when Drogheda fell (and many civilians were killed in the sack of Drogheda). The brutality did not end with the defeat of the Irish armies; guerrilla warfare brought continued violence with, as usual, most of the suffering borne by civilians. Cromwellian rule brought a wave of anti-Catholic legislation and institutionalised repression. The (Catholic) Irish remember Cromwell as a brutal conqueror and tyrant.

From the English perspective, Cromwell is often seen as a supporter of the people who overthrew a tyrannical king, and a friend of religious freedom. To the Scots and especially the Irish, he is a foreign conqueror who wrought destruction with fire and sword and an enemy of religious freedom.