The Greys were originally a proud nation of powerful fighters. Unfortunately for them, their pride would be their downfall. When they were invaded by the Tan Republic, they were too proud to ask the Green Nation for help, leading to most of their territories being conquered by the superior might of the Tans.
With most of their country under Tan control, the Greys shifted to using guerrilla warfare against the Tans, as well as to fight any other enemies they had.
While attempting to outflank the Tan Army, Sarge found himself on the Grey-Tan border. Because the Greys were at war with both the Greens and the Tans, this resulted in a three-way skirmish between the nations.
Army Men: Sarge's Heroes
Grey Soldiers appear as prisoners of the Tan Republic that can be freed by Sarge to help him rescue Sharp.
Army Men: Sarge's Heroes 2
Dr. Madd, a Grey scientist, is an ally of the Tan Republic in this game, and has several Grey Soldiers working under him.
Two Grey Soldiers later attempt to fight back against the Tan Army during their invasion but to no avail.