Moctezuma: Aztec Ruler, British Museum

History is written in blood, however elegant the cover. Nowhere is this more apparent than in the collapse in 1521 of the Aztec Empire, a culture that presented Europe with a vision of such otherness that it could only be destroyed. In 2002, the Royal Academy of Arts tried to persuade us to look beyond the grisly tales of human sacrifice to a more nuanced portrait of a people steeped in gory rituals that we, soaked in the serial-killer television porn of the 21st century, might strangely understand.

It didn’t work – how many vessels designed to receive still-beating human hearts do you need to see before turning away? This new exhibition, the latest in a stunning series at the British Museum about great rulers (pleasing whiffs of unapologetic History with a capital H), tries its best to give us Moctezuma, man of his times, the last Aztec ruler. Set in the dome of the splendid Reading Room, the exhibition charts a course through this fated man's social, cultural and political setting, and the sheer materiality of the objects on display (turquoise masks, stone thrones, obsidian knives, gold jewellery, delicate parchments) is gripping.

The picture that emerges is of a ruler who couldn’t stop the inevitable – an entire people subjected to the brutal hand of Hernán Cortés, the bearded adventurer whose ambition it was to conquer the Mexican territories for his Spanish sovereign. Tenochtitlan, the capital of the Mexica people (as the Aztecs are properly known), was simply extraordinary. Bernal Diaz, one of Cortés’ lieutenants, records in his famous journal of the Conquest that Tenochtitlan appeared to them as a new Venice. At 250,000 inhabitants, it was larger than any city in Europe at the time and, the Spanish knew, it was rich with gold and precious artefacts. He notes how clean and efficiently organised the city was, once they had been welcomed, albeit with great caution, into its gates by Moctezuma.

Once inside, the Spanish were incredulous: how could such a society construct a complex city, compute complex astrological equations, organise huge irrigation systems to feed large populations, and achieve land reclamation on this scale? But for all the Mexica's skills, there were technological gaps such as the absence of metal-smithing and the wheel. It is also hard for us to comprehend the Mexica view of history: every 52 years, they buried their main temples in another temple, erasing the events of the previous epoch or rewriting them as politics or ritual required. It was as if the world could be reinvented afresh. But at great cost.

Diaz writes with moving incredulity of the rivers of blood that flowed from the temple mounts, the heart-rending cries of the victims, the hideous appearance of the priests with their hair matted with dried blood and charcoal blackened skin. He was, he realised with growing horror, in a land that had not even existed on medieval maps nor been mentioned in the Bible.

Maurice Collis’ 1954 biography Cortes and Montezuma (the latter’s name is now corrected) gave us a soft-eyed king, a yielding sacrifice. This exhibition suggests instead a theocracy so captivated by its ritual calendars, omens and hierarchical complexity it failed to adapt to the fast-changing realpolitik thrust upon them by the Spanish - mysterious half-men, half-horse creatures emerging from tall ships and stir-crazy for gold. The contemporary descriptions, some movingly illustrated with quick sketches, of Moctezuma’s slide from semi-divine figure to pathetic captive, chained at the neck, are heart-rending, appropriately.

Looking at the large model of Tenochtitlan, showing numerous temple podia where hapless victims had their hearts torn out, I couldn’t help thinking of the current Labour Party Conference, where the swish of knives falling is faintly heard. This exhibition is beautifully designed, with echoes of Mexico City’s Hotel Camino Real, designed by fun-boy Ricardo Legorreta in 1968, and it does its best to keep the blood off the carpet, maintaining an authoritative, emotionless tone throughout. Facts - yes. Heart - not much.

Moctezuma: Aztec Ruler continues at The British Museum until 24 January 2010. British Museum website here

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