Two hundred years ago, Napoleon launched an invasion that would change Europe – and warfare – for ever. Now the Spanish are celebrating what some see as their finest hour.

Brutality was nonetheless laced with heroism, which is why the Spanish War (as the French call it) became – despite the loss of an estimated million lives – a romanticised episode in Spain's collective memory, a brief precious moment of glory that today everyone seeks to reclaim. This is hardly surprising, since for the subsequent two centuries Spain suffered the loss of a world empire, civil wars, military coups and a role on the world stage that dwindled to insignificance.

Hence the enthusiasm with which Spain prepares to mark this year's 200th anniversary. But the forthcoming festivities, re-enactments, official parades, exhibitions and book launches are likely, to British eyes, to have a peculiarly missing centre. Where, we may ask, is the Duke of Wellington, perhaps the greatest general Britain ever produced, whose tens of thousands of crack troops deployed for seven years in Spain and Portugal were never vanquished?

The Prado museum is restoring the two great works as the centrepiece of a forthcoming exhibition, Goya in Times of War. Goya's drawings, Disasters of War, begun in 1810 at the height of the bloodshed, capture precise episodes with a timeless quality that applies to all wars.

They show "universal human behaviour", says Jose Manuel Matilla, the head of the Prado Museum's department of drawings and prints. "Goya's Disasters mark the maximum expression an artist has ever achieved of the irrationality of violence and its terrible human consequences." The works were shunned in the artist's lifetime. No one wanted such stark documentary records of cruelty perpetrated by both soldiers and civilians. They remained in his family for decades and entered the Prado after 1860.