When the conquest of Ireland was completed, Cromwell hastened to London to receive the thanks of parliament and the acclamations of the people; and then he hurried to Scotland to do battle with the Scots, who had made a treaty with the king, and were resolved to establish Presbyterianism and royalty. Cromwell now superseded Fairfax, and was created captain-general of the forces of the commonwealth. Cromwell passed the borders, reached Edinburgh without molestation, and then advanced on the Scotch army of twenty-seven thousand men, under Lesley, at Dunbar, where was fought a most desperate battle, but which Cromwell gained with marvellous intrepidity and skill. Three thousand men were killed, and ten thousand taken prisoners, and the hopes of the Scots blasted. The lord-general made a halt, and the whole army sang the one hundred and seventeenth psalm, and then advanced upon the capital, which opened its gates. Glasgow followed the example; the whole south of Scotland submitted; while the king fled towards the Highlands, but soon rallied, and even took the bold resolution of marching into England, while Cromwell was besieging Perth. Charles reached Worcester before he was overtaken, established himself with sixteen thousand men, but was attacked by Cromwell, was defeated, and with difficulty fled. He reached France, however, and quietly rested until he was brought back by General Monk.
With the battle of Worcester, September 3, 1651, which Cromwell called his "crowning mercy," ended his military life. From that day to the time when be became protector, the most noticeable point in his history is his conduct towards the parliament. And this conduct is the most objectionable part of his life and character; for in this he violated the very principles he originally professed, and committed the same usurpations which he condemned in Charles I. Here he was not true to himself or his cause. Here he laid himself open to the censure of all posterity; and although he had great excuses, and his course has many palliations, still it would seem a mockery of all moral distinctions not to condemn in him what we would condemn in another, or what Cromwell himself condemned in the murdered king. It is true he did not, at once, turn usurper, not until circumstances seemed to warrant the usurpation--the utter impossibility of governing England, except by exercising the rights and privileges of an absolute monarch. On the principles of expediency, he has been vindicated, and will be vindicated, so long as his cause is advocated by partisan historians, or expediency itself is advocated as a rule of life.