(Sept. 3, 1650), decisive engagement in the English Civil Wars, in which English troops commanded by Oliver Cromwell (Cromwell, Oliver) defeated the Scottish army, thereby opening Scotland to 10 years of English occupation and rule.

The execution of Charles I, king of England, Scotland, and Ireland, in January 1649 created a constitutional crisis. While England became a republic, the rest of Charles's dominions—including five colonies in North America—recognized his eldest surviving son, Charles II, as king. The Scots mobilized an army to press his claims, but in June 1650 Cromwell decided on a preemptive strike and led the army of the English Republic toward Edinburgh. He soon laid siege to the city, but in August torrential rain, shortage of food, and the proximity of the Scottish army under David Leslie in a strongly fortified camp forced the English to retreat eastward to the port city of Dunbar. There, Cromwell found an English flotilla that supplied his troops with tents and provisions; Leslie, meanwhile, moved his troops to a commanding position on a hill overlooking Dunbar, pinning Cromwell down. On September 2, the Scots moved down the hill in preparation for an all-out attack.

Cromwell's practiced eye immediately spotted two weaknesses in the Scottish troop deployment. First, the Scottish left wing was crowded against a steep slope that prevented maneuvering; second, a slight depression created some “dead ground,” or a natural trench, in front of Leslie's position that enabled Cromwell's troops to redeploy under cover. That night, therefore, despite driving rain, English troops moved in front of the Scottish line to create an overwhelming superiority against their right wing. At dawn the following day, shouting a biblical quotation, “Now let God arise, and his enemies shall be scattered” (Numbers 10:35), Cromwell launched his attack. The battle was over in an hour—fewer than 100 Englishmen perished, against some 3,000 Scots killed and about 10,000 made prisoners.

Southern Scotland now surrendered to the English, who abolished all native institutions of government and created a new administration at Dalkeith, just outside Edinburgh, to rule the conquered territory. Within two years, the Scottish Highlands and Islands had also been brought under English control. For the first time, England, Scotland, and Ireland became part of a single state, a republic ruled by a single government (in London) that sent elected representatives to a single parliament (in Westminster). This integration depended entirely on force, however—10,000 English troops occupied Scotland. The return of Charles II in 1660, two years after Cromwell's death and 10 years after Dunbar, led to the demobilization of the Republican Army and the restoration of separate governments in Edinburgh and Dublin.