Amidst the energy crisis in the 21st century, the energy-rich countries of Venezuela, Brazil, and Chile United to form the Federation of the Americas. Diego Almagro was appointed to be the leader of the newly formed Federation. Under his leadership, Almagro expanded the Federation all throughout South America, conquering country after country. Almagro was highly Anti-American, and ordered the execution or imprisonment of all U.S.-born individuals within the conquered territories, drawing the wrath of the United States.
Ghosts' leader, Captain Gabriel Rorke, convinced the U.S. leadership to send the Ghosts into Venezuela to assassinate Almagro in the hopes that this would lead to the collapse of the Federation. The Ghosts are successful in killing Almagro, but his death failed to halt the expansion of the Federation into a global superpower.
Additionally, Lieutenant Elias Walker was forced to abandon Rorke during the mission. This resulted in him being captured by the Federation and converted through the Amazonian torture techniques into a Federation field commander and the most dangerous threat that the Ghosts ever faced.
- In one of Rorke's files, Elias refers to Almagro as "the leader of the Federation," even though he was only a military man.
- Diego will die in one shot, regardless of wherever shot and whatever weapon used.
- His name is most likely a reference to Diego de Almagro, a Spanish conquistador who participated in the Spanish conquest of Peru.