France was resolved to change its harrowing state of affairs, growing weary of the Madjriti oppression on Atlantic voyages and intent on solving the conundrum of whether Al-Mamlakat Al-Raabiea (El-Rabeeah, the Fourth Realm) was a new continent or merely an unseen part of Asia. The French crown thus procured the resources for an expedition, led by Chevalier Jean-Baptiste de Morny, who set sail in March 1555. De Morny, deeply fearful of the Islamic world, viewed his expedition as a holy mission against the "Mohammadien Scourge". Shortly after paying Madjriti taxes, a severe storm in the Mid-Atlantic pushed the fleet off course; despite the distress of his men, De Morny refused to turn back.

The fleet eventually made landfall on June 5th, 1555, on a mysterious, forested, and humid coast. The terrain seemed unremarkable, and the arduous trek north through the endless, challenging jungle, which the French referred to as the "Green Hell," dismayed the explorers. They eventually encountered native groups they called les Cotiers (the native peoples of the Yucatan, remnants of the Mayan Civilization), who were agricultural and connected by an extensive trade network. Discovering grand, derelict stone structures and temples that reminded them of the pyramids in Egypt, the French were convinced an advanced civilization existed nearby.

As the expedition continued northwest, the French followed whispers and tall tales of this elusive society, eventually discovering a sophisticated city on artificial, reclaimed land on Christmas Day. This was the capital of the Les Lacustres (The Lake People, corresponding to the Mexica/Aztec civilization), whose grand temple confirmed they were the builders of the derelict structures. De Morny, deeply pious, became convinced that the Lacustres were devout Christians—perhaps like the fabled Prester John—and thus the key to defeating the Muslim powers in Europe. This hope was shattered when the Emperor summarily rejected De Morny's proclamation of Christ, and a French priest was shouted at for attempting to install a cross.

De Morny initially rationalized the rejection as resulting from his own intolerance or a simple difference in Christian sect. However, his true realization occurred when the French witnessed the Lacustres committing horrific rituals by torturing and sacrificing prisoners in their temple. Through interpreters, De Morny learned that the Lacustres habitually invaded neighboring lands, taking people for tribute to be sacrificed. This led De Morny to conclude that the Lacustres were merely "savages with the veneer of high civilization" and the true "Mohammadien Scourge" of the New World. He resolved to pacify the land by the sword, motivating his soldiers with the prospect of seizing the Lacustres' rumored hoarded gold. After failed attempts to court local peoples, the French secured a crucial alliance in January 1557 with the militarily formidable Rocalleux (the Tlaxcaltec people), forming an army of 8,000 men.

The joint French and Rocalleux forces marched on the capital but were quickly ambushed and forced to retreat by March 25th, 1557. Observing the city's strangely stoic and weakened state—a result of Old World diseases—De Morny ceased direct assault and began a merciless artillery bombardment on April 4th, shelling the timber city into submission. The French captured the temple and the emperor on May 2nd, but immediately faced a critical blow when the Rocalleux betrayed them and began slaughtering the French forces throughout the rest of the month. The French expedition neared decimation until, on June 3rd, a random artillery firing killed the Rocalleux commander. The leaderless Rocalleux routed, and the French ruthlessly pursued and annihilated them, securing victory by July 14th after immense casualties on both sides.