ZAC 1957
King Helic Muroa unites Delpoi, the Central Continent of Planet Zi. The same year, the king's eldest son, Helic II, is born.

ZAC 1959
A second son, Zenebas, is born to King Helic.

ZAC 1978
King Helic dies. Helic II takes over the government, abolishes the monarchy, establishes the Helic Republic, and becomes president. Zenebas becomes the supreme commander of the military, but a feud develops between the more moderate president and the warlike Zenebas, who plans to invade other continents. In the same year, Zenebas rebels against the Republic and establishes the Zenebas Empire to the west of the Central Continent. He proclaimes himself Emperor. In the following year, war breaks out between the Republic and the Empire. Both armies send metallic lifeforms that had once been used as livestock, Zoids, to the battlefront.

ZAC 2029
Globally III, a pioneer spaceship from Earth, makes an emergency landing on the Central Continent, where a longstanding war has been taking place. Overwhelming technology is brought to a civilization comparable to the middle ages, and the fighting grows increasingly fierce.

ZAC 2051
The Zenebas Empire falls. In the same year, the Guylos Empire of the Dark Continent of Nyx, which absorbed the remnants of Zenebas' defeated soldiers, declares war on the Helic Republic.

ZAC 2056
A giant comet crashes into Planet Zi. The world is hit by a major catastrophe, and both armies are unable to continue the war.

ZAC 2099
After more than 40 years, the Guylos Empire declares war on the Helic Republic once again.

ZAC 2102
Gunther Prozen, regent of the Guylos Empire and son of the late Emperor Zenebas, begins a rebellion in the capital of the Guylos Empire, blowing himself up along with the main forces of the Guylos and Helic armies. In the same year, Prozen's son, Wolff Muroa, takes control of the Central Continent. The Neo Zenebas Empire is founded. In the same year, the remaining forces of the Republican Army organize a resistance force, demonstrating their determination to fight against the Empire until the very end.