Inspired by my most recent game of Civilization V. This is exactly what happened in-game. Civilizations and Great Person names are randomly assigned to every player, so it's a big coincidence that I got to play the Aztecs. For anyone who hasn't played the game, this is more or less what can happen if you're aiming for a Domination Victory (a.k.a. Last Man Standing)
In the second half of the XIX century, the Aztec army, led by Khalid ibn al-Walid has occupied the french city of Orleans. The catapults, longbows and pikes of this new land are no match for the battleships and 88mm artillery cannons.
Napoleon, worried by the presence of semiautomatic gatling guns in the borders, offers Consul Montezuma a peace treaty, so that hostilities will cease for a minimum of 100 years.
But in the Old continent, Tenochtitlan is living a Golden Age withendless prosperity, the Aztec's main religion (Buddhism) has spread to Paris and Thomas Alva Edison has recently founded the world's greatest Academy in Beijing (which is also part of the Empire)
Put it simply, the Empire that bested Queen Elizabeth and Wu Zetiang has nothing to lose.
Montezuma negotiaties with Napoleon the pacific surrender of the lone island of Tours and a small wine tribute (to appease the rabble in London) in exchange of retiring the troops from the border. For Napoleon, this is too high a price: Tours may be a small settling, but has great potential because of its prime maritime location; wine on the other hand is the only export that keeps the French economy afloat.
Napoleon declines Montezuma's unfair peace offer and in response, war is declared between the two Civilizations for the second time in less than 50 years.
The French Army is called back home to Paris and catapults are ready to fire at any moment. But the Infantry suffered heavy casualties during the defense of Orleans and morale is lower than ever. The factories in Texcoco keep shipping gatling guns and reinforcements are already on their way to the French territories. In a matter of months, Paris and Lyon are surrounded by long range cannons, well beyond the catapults' effective range. Montezuma negotiates with Napoleon once more and once more his demands are denied.
Napoleon calls for help to his allies in the City States of Genoa, Zanzibar, Tyre and Venice, but the call falls on deaf ears. They all are next to or surrounded by Aztec cities and protectorates and at this point war means suicide. One week after the second denial of Napoleon, Aztec ambassadors arrive to these Cities with a special message from the Consul. He offers the cease of tributes to Tenochtitlan and a gift in gold so that they keep neutral in this war. The conquest of Beijing gave the Empire vast amounts of gold and other treasures that eclipse the French's.
Hostilities were terribly one-sided, which had the dubious advantage of making of this a short war. The walls that defended Paris from the barbarian tribes since its foundation are now falling under the constant attack of an enemy that cannot be counter-attacked. The Longbowmen and Pikemen charge bravely to try and reach the invasors, but they are outnumbered by riflemen.
Two years later, General Khalid ibn al-Walid climbs to the top of the Paris Colossus and raises a Quetzal-feathered flag, symbol of the Aztec conquest. Only one week prior, French reinforcements arrived to Lyon only to find it completely razed. The triremes looked like a museum piece next to the iron battleships, their crew surrendered without hesitation.
Consul Montezuma himself traveled to Paris to celebrate the coming of the New Century. That night he gave a speech about the State of the Empire and the plans for the newly discovered technology of flight. It took the Aztecs 5000 years to go from a rock-slinging tribe to the only Civilization in the whole world.