In the annals of the Napoleonic Wars, the Peninsula War stands as a testament to the indefatigable spirit of resistance against the tyrannies of overreaching power. From 1808 to 1814, the rugged landscapes of Spain and Portugal became the stage for a fierce conflict between Napoleon's vast empire and those who dared defy his Continental System. England, that sceptred isle, set across the channel from the sprawling continental ambitions of the French, stood as a beacon of resistance.

The origins of the Peninsula War can be traced back to the Treaty of Fontainebleau in 1807, where Napoleon and Spain decided to divide and conquer Portugal. The pretext? Portugal's refusal to comply with the Continental System which aimed to cripple British trade. However, true to the often-duplicitous nature of politics of the day, the real French aim was to turn on their Spanish allies and install Joseph Bonaparte, Napoleon’s brother, as the monarch of Spain. This led to the Peninsula being inflamed in anti-French uprisings.

British involvement began in August 1808 under the leadership of Sir Arthur Wellesley, later the Duke of Wellington. Wellesley, a commander of unparalleled strategic acumen, first tasted victory at the Battle of Vimeiro on 21 August 1808. This victory forced the signing of the Convention of Sintra, a controversial agreement which allowed the defeated French to be evacuated with all their spoils.

The years that followed saw a series of fiercely contested battles. Napoleon himself entered Spain with a massive force in late 1808, pushing back the British to the edges of the Iberian Peninsula. Yet, the British, Portuguese, and Spanish forces, through a series of guerrilla tactics and engagements, continuously harassed the French.

Commanders on both sides exhibited both brilliance and folly. The Duke of Wellington's strategies, including his construction of the Lines of Torres Vedras, a series of fortifications to protect Lisbon, showed his unparalleled defensive genius. Opposing him were capable French marshals like André Masséna, Nicolas Jean-de-Dieu Soult, and Auguste Marmont. Yet, they struggled against the combined might of British redcoats, Spanish guerrillas, and Portuguese defenders.

Amongst the various pivotal battles, the Siege of Badajoz (16 March – 6 April 1812) stands out. It was a brutal episode, where British forces encountered immense difficulties in breaching the fortified town's walls. When they eventually did, the subsequent sacking of Badajoz showed the grim side of warfare.

Salamanca, fought on 22 July 1812, was another critical battle. Wellington's brilliant manoeuvring led to a decisive British victory and allowed for the capture of Madrid. The French were driven back, but the war was far from over.

By 1814, after continuous battles, sieges, and countless hardships faced by both soldiers and civilians, the Peninsula War came to its conclusion. The war saw British forces emerge victorious, with the French expelled from the Iberian Peninsula. Wellington’s triumphs in the Peninsula made him a national hero and set the stage for the larger confrontation at Waterloo in 1815.

Looking back, the Peninsula War, with its mix of conventional battles and guerrilla warfare, was a war of endurance, will, and strategy. The British, along with their Spanish and Portuguese allies, showcased the spirit of resistance and determination. In the words of the ever-eloquent Churchill, they proved that "however vast the darkness, we must supply our own light."