The Battle of Dunbar (3 Sept. 1650) was the first of two battles that marked the culmination of Oliver Cromwell's military career. "Essential Agony" also contains accounts of three other key battles Cromwell fought against the Scots and their royalist allies in 1648, 1650, and 1651. The wider background here is thus the collapse of the British and Irish monarchy and the creation and protection of the first modern republic and Free State in 1648–53. The author, military historian Arran Johnston, founder of the Scottish Battlefields Trust, lives in Dunbar, where Cromwell was based on the eve of the battle.[1]

The book consists of a prologue, eight chapters, and an epilogue. Chapter 1 sets the background of Cromwell's involvement with Scotland by exploring the Battle of Preston (17–19 Aug. 1648). Chapters 2–3 concern the period from 1649 onward, when the son of the executed king, Charles I, sought to conquer his father's former kingdoms with the assistance of the Scots. Chapters 4–7 are dedicated to Cromwell's invasion of Scotland in summer 1650 and the campaign leading to the battle just south of Dunbar. Chapter 8 covers the military and political aftermath of that battle. The epilogue looks at the 1651 campaign when Charles Stuart and his Scottish allies in turn invaded England, only to be decisively beaten by Cromwell at Worcester exactly one year after the victory at Dunbar.

This highly complex story demonstrates why "English Civil War" is an entirely inappropriate designation for the intertwined mid-seventeenth-century conflicts in Britain and Ireland. By the time of the Battle of Preston, with which the book begins, there had been three interlocking conflicts within Britain as a war was raging across Ireland. Shifting alliances, both large-scale and personal, had changed the face of the wars since 1639. However, the story of the civil war was one of revolution. Initially, war broke out between the Scots and their sovereign because he had interfered with their Presbyterian Church structure. But during the two conflicts, known as the first and second Bishop's Wars, a political revolution took place and the king's status was downgraded to a kind of constitutional monarch. This affected the king's English and Welsh subjects, whose desire for an equally dramatic political change led to war in England and Wales. Frustration at being excluded from these political reforms because of its colonial status led to a rebellion in Ireland. By the end of 1643, the Scots had allied with the Westminster parliament and defeated the king by 1646; following a brief peace, they turned on their erstwhile allies and supported the king in a new war. During this fifth conflict, Lt. Gen. Oliver Cromwell, second in command of the English New Model Army, defeated royalists in Wales before confronting the invading Scots at Preston. The fifth war ended in a catastrophic defeat for King Charles and the Scots and led to the king's trial and execution.

Following the king's death, England and Wales were declared a republic and Free State and Cromwell was sent to bring Ireland (regarded as an adjunct of the English state) into line. Scotland, as an independent nation, was not incorporated into the republic and instead declared the dead king's son to be his lawful successor as King Charles II of Great Britain. This and other provocations led to a state of war between Scotland and the republic. Having returned from Ireland, Cromwell was promoted to Captain General and sent to forestall a potential fourth Scottish invasion of England. Dunbar was the major battle of the first year of this war.

The author details preparations for war by both Cromwell and the Scots in summer 1650. For the latter, this entailed marshaling resources for the army and organizing the countryside between Edinburgh and the border with England in order to deny resources to Cromwell's army. Johnston analyzes not only this aspect of the preparations but the nature of the warfare and the make-up and structure of the Scottish army, especially with regard to the reforms of 1650.

In this period, armies were usually disbanded after conflicts; this was especially true of Scotland, but not of England, where the new state felt threatened by external and internal opponents. Johnston also shows that the army Cromwell was to command was assembled from veteran regiments during that summer. He deals with assessments of the rival commanders in some detail as well.

For most readers of such a book, Oliver Cromwell will be a familiar figure. Not so his opponent. Lt. Gen. David Leslie had fought on the European continent and he was second in command of the army Lord Gen. Alexander Leslie (hereafter, Lord Leven) led into England in 1644. At the Battle of Marston Moor (2 July 1644), he seconded Cromwell on the left wing of the parliamentarian/Scottish army. He also defeated royalist forces in Scotland in 1645. Leslie had avoided involvement in the 1648 war, because he was politically opposed to supporting Charles I at that point. With Lord Leven beginning to feel his age in 1650, Leslie, though technically his second, was to be the commander in the field. As Johnston demonstrates, he was well suited to command and his campaign was an outstanding success (chaps. 3–4). Cromwell was kept out of Edinburgh and forced to rely on supplies brought in by sea and road from England. By early September, he had been pushed back to Dunbar and his army was suffering the widespread effects of illness.

Johnston's meticulous account of the campaign reflects his intimate knowledge of the countryside and its roads. It gives the reader a vivid sense of just how seventeenth-century armies moved and provisioned themselves on campaign. The granular description of Leslie's failure at the Battle of Dunbar is most welcome, because his—and his army's—performance had to that point been commendable. The author also explains the role of government representatives who questioned and interfered with Leslie's decisions and even his command structure.

Leslie is presented as aggressive in his plans to attack Cromwell at Dunbar, rather than (as is sometimes claimed) passively waiting for him either to try to break out southwards along the road to England or to begin to evacuate his army via Dunbar harbor. The strategic discussions within Cromwell's command are covered as well. But the centerpiece of the book is its depiction of the battle itself. We learn about each army's deployment and the Historic Environment Scotland's recent attempt to redefine that alignment by shifting the battle lines through ninety degrees. Johnston rejects this interpretation, based on his deep involvement in the modern signposting of the battlefield. The same expertise informs the book's twelve maps. Minor defects include poor proof-reading and the unfortunate lack of an index.

"Essential Agony" should now be mandatory reading for anyone interested in seventeenth-century warfare and the careers of Oliver Cromwell and David Leslie.