Oyo Empire metropolitan Oyo. This may have been fine in the 15th century when Oyo controlled only its heartland. But to make and maintain farther conquest, the structure underwent several changes. Oyo maintained a semi-standing army of specialist cavalry soldiers called the "Eso", the "Esho" or, formally, the Eso of Ikoyi. These were 70 junior war chiefs who were nominated by the Oyo Mesi and confirmed by the Alaafin of Oyo. The Eso were appointed for their military skill without regard to heritage and were led by the Are-Ona-Kakanfo. After Oyo's return from exile, the post of Are-Ona-Kakanfo was established as the
Empire: Wargame of the Century interface. Starting around 1987, "Empire: Wargame of the Century" on the Atari ST, Amiga, Commodore 64, Apple II, Macintosh and DOS was produced. In its review of the game, "Computer Gaming World" noted the improved UI, saying "the playability of an already successful system has been significantly enhanced". The game would later receive the magazine's "Game of the Year" award for 1988; in 1989 the magazine named "Empire" to its Hall of Fame for games readers rated highly over time, with a final score of 9.71 out of 12, in 1990 readers voted for the game as their "All-Time Favorite",