In 1815 Napoleon made a last desperate attempt to persuade Europe to accept him rather than the Bourbons as ruler of France. When Britain, Austria, Russia and Prussia agreed to invade France to remove him he chose the last possible moment to attack the British and Prussians in Belgium, hoping to separate them and capture Brussels without fighting or defeat each in turn. He achieved sufficient surprise to come close to success on 16 June, but his plans required a smoother-running machine than his army provided: poor staff-work, distrust, weary cynicism and some treachery undermined French efforts and the encounters at Quatre Bras and Ligny ended in a draw and a narrow victory. On 17 June Napoleon failed to crush Wellington before the weather intervened to ruin his pursuit. Wellington withdrew his army skilfully to a chosen position where Blücher promised to join him. Napoleon underestimated the dogged determination of his enemies to support each other and the Prussians outmarched Grouchy to arrive in time to transform Wellington’s well-organised, stubborn and brave defence at Waterloo into a crushing victory. After this catastrophic defeat Napoleon had again to abdicate.

Between 1808 and 1814 Spain and Portugal were devastated by the single most destructive episode of the Napoleonic Wars, namely the so-called Peninsular War. Originating in a foolhardy attempt on the part of Napoleon to render the former country a more reliable ally in the wake of his bloodless occupation of the latter in October 1807, this soon turned sour. French armies sustained one embarrassing reverse after another; assailed by multiple problems, the puppet regime of Joseph Bonaparte was unable to impose its authority; the Spanish armies proved easy to beat but hard to eliminate; the British ejected the French from Portugal and turned her into an unassailable stronghold; the French suffered heavy casualties; and political revolution in Spain made it very hard to claim the ideological high ground. Had Napoleon been willing to concentrate all his efforts on the struggle, he might yet have prevailed, but his decision to attack Russia badly destabilised the position of his armies, the result being that within two years the whole of the Peninsula had been liberated. All this makes for a dramatic story, but in practice the impact of the Peninsular War on the fate of Napoleon was very limited, its real importance lying rather in its influence on the history of Spain and Portugal.

The British Army took part in numerous operations, ranging from small expeditions to the West Indies, Africa and along the European littoral to major operations in Portugal, Spain and Belgium. Initial struggles with these responsibilities, together with those of imperial policing and maintaining order in Ireland would oblige the Army to implement extensive reforms, particularly in tactics and unit organisation, even while the system of purchase for officers remained intact. While British infantry produced mixed results in the field during the French Revolutionary Wars, in time it became noteworthy for its musketry and remarkable doggedness in battle. Chronically understrength and notoriously difficult to control, the cavalry tended to play only a minor part on campaign, while shortages of artillery and engineers plagued the Army throughout this period. Albeit comparatively small, in creating an Iberian foothold which soon developed into a major theatre of operations, the instrument forged in the battles and sieges of the Peninsula and southern France helped drain Napoleon’s resources over a substantial period and established the high standard of battlefield performance which was to reach its apogee on the field of Waterloo, from which would emerge one of history’s greatest commanders – the Duke of Wellington.