Kratos' Army was with Kratos on the day of the immense battle with the Barbarians. As shown throughout the series, it was here that he was indebted to Ares, the god of war. They fought valiantly, but were easily overpowered by the ruthless tribes of barbarians until Ares gave him the ability to slaughter his enemies. It's also safe to assume that his former Spartan soldiers were also the soldiers who followed him on his reign of terror during his servitude to Ares.