After Sazer-X traveled back in time to the year 2005 to halt the Descal Fleet's original invasion, the Neo Descal fleet also traveled back in time to stop them from interfering in the invasion.
They saved the Three Shoguns after their flagship was destroyed by Sazer-X. Despite their incompetence, Neo Descal's generals kept them around to prevent any alterations to the timeline. The invasion of Earth was initially spearheaded by Grouza and Garade, but after their continued failures the leader of Neo Descal, King Neo Descal himself, arrived to take over the war effort.
They were ultimately destroyed after King Neo Descal was defeated and Neo Descal's invasion of Earth was stopped, cancelling out the future where Neo Descal conquered Earth.