Almost 500 years after European adventurers dressed him up as a collaborator and stole his throne, the British Museum is preparing to rehabilitate one of history’s great rulers.

Moctezuma II, or Montezuma as he is often called today, was the last elected Aztec emperor and a formidable warrior regarded by his subjects as a semi-divine figure who ruled over a politically complex empire that stretched from the shores of the Pacific to the Gulf of Mexico. However, posterity knows him mostly as the man with the misfortune to be in charge when Hernán Cortés’s conquistadors arrived in Mexico in 1519, a gaudy but primitive potentate who gave up his people’s independence voluntarily and paved the way for centuries of Spanish rule.

Moctezuma, Aztec Ruler, opening in September, will attempt to correct that notion by emphasising his enormous achievements in the 20 years before Europeans landed on Mexican soil and by arguing that he was forcibly and illegally deposed, not a willing dupe.

It is the fourth and final instalment in a series of exhibitions at the museum examining the nature of power through individual rulers: the First Emperor of China (represented by the historic loan of 20 Terracotta Warriors), the Roman emperor Hadrian and, currently running, Shah Abbas of Iran.

To put together the first ever exhibition dedicated to Moctezuma, the museum has drawn on collections in Mexico, Europe and the US as well as its own Aztec artefacts.

The empire and its conquest will be examined through 132 objects, most of which have never been to London. They include exquisite goldwork, mosaic items, monumental sculptures, enconchados (oil paintings on wooden panels with inlaid mother of pearl details) and the European paintings from the period which helped to shape (misleadingly, the curators suggest) our understanding of Moctezuma and his world.

Neil MacGregor, the director of the museum, said that the show would achieve “what the museum has been trying to do for 250 years: to present the history of the world from another place.”

“We are trying to look at an absolutely key moment through the filter of one great man who was running an extraordinarily sophisticated empire in a way that to Europeans was very strange.”

Moctezuma ruled from 1502 to 1520 and consolidated Aztec power as never before. He won victories that extended the empire’s borders, reorganised the court and built a new palace in the heart of Tenochtitlan (modern day Mexico City), creating a capital that was described by one European visitor as “the Venice of the Americas”.

By all accounts, he was a formidable leader at the peak of his power when Cortés’ band of a few hundred men arrived. Moctezuma received them cordially but what happened next is disputed.

Conventional history portrays him as welcoming the Spanish into Tenochtitlan, housing them and then appearing on a palace balcony before an angry mob to defend them, whereupon he was stoned to death by his own people.

Colin McEwan, head of the British Museum’s America’s section, said that this view dates back to Cortes’ own propaganda, designed to legitimise Spanish claims to the wealthy new territory.

Even in Mexico it has poisoned the emperor’s reputation; there are no monuments to him in his homeland. “We will interrogate this received wisdom and reveal another story that has yet to be told,” Mr McEwan said.

Specifically the exhibition will present Moctezuma as a hostage, not a collaborator. “We are opening that can of worms, saying he was defeated, yes, but willingly? No. He was forced out under duress.”

Two little-known 17th century images, which have not been exhibited before, support this reinterpretation by depicting Moctezuma on the balcony as a Spanish captive. The Tlaxcala, an illustrated book in Glasgow University’s collection shows the emperor being beaten with a chain while the Codex Moctezuma, held in Cuernavaca, Mexico has him with a rope around his neck.

After Moctezuma’s death, possibly at the hands of his Spanish guests rather than his subjects, there followed a year of fierce warfare before the Aztec empire fell.

The seeds of its collapse lay in its unusual structure, Mr MacGregor said. Unlike most empires in the Old World which attempted to impose a beauracracy on their territories, the Aztecs based theirs on regular payments of tribute, such as the stunning turquoise mask that will be the emblem of the exhibition. But without its charismatic figurehead, the empire was a hollow edifice and crumbled accordingly. “It wasn’t really the Spaniards who conquered Mexico. It was the disaffected peoples who allied with the Spanish because they were fed up with paying these inordinately heavy levies.”

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