The Apokolips Civil War was the conflict that resulted from the power vacuum following the death of Darkseid, the dread lord of Apokolips, after battling Superman and the Justice League on Brainiac's asteroid.
Darkseid's inner circle was unsure on what happened to their lord and master. Though Kalibak, Darkseid's son, would have normally succeeded his father to the throne, he was deemed too dimwitted to rule. Additionally, the other major power brokers on Apokolips, Desaad and General Steppenwolf, had died the same day as Darkseid through unrelated events.
With the resulting power vacuum, the Darkseid loyalist faction rallied around Granny Goodness, while Virman Vundabar formed his own army with Kanto and Mantis. Vundabar managed to capture Kalibak, so Granny Goodness coerced Mr. Miracle and Big Barda, her former charges, to rescue Kalibak by kidnapping Mr. Miracle's manager Oberon. J'onn J'onzz was reluctant to involve the Justice League since the civil war kept Apokolips' would-be rulers too busy to threaten Earth, but Flash helped free Kalibak and rescue Oberon. Kalibak was then imprisoned on Earth in order to allow the struggle to continue.
A year later, Goodness and Vundabar's forces were prepared for a final battle for control of Apokolips when the recently resurrected Darkseid teleported onto the battle field. Both factions immediately repledged their loyalty to him and he launched his forces against Earth.