Kreutz was a warrior who served under Geil Rugner during the War of Succession, having served Geil since his youth. As such, he sometimes referred to Geil by his old name, Georg. Loyal to Geil, Kreutz was considered the only truly great leader in his oppressive government. He was a rival of Humphrey Mintz and was gravely wounded by him during the war.
Following the death of Geil and the ascension of Barbarosa Rugner to the throne, Kreutz made his way to Dragon Knight's Domain and secluded himself. As an autonomous region recognized by the Scarlet Moon Empire, he was safe from extradition and reprisal there. Even years later, he still considered Geil to be his only master.
There, during the height of the Gate Rune War, his former rival from the War of Succession, Humphrey, invited him to join the Toran Liberation Army, considering him Geil Rugner's greatest general. Though initially taken aback, Kreutz accepted this offer only for the chance to kill Barbarosa and avenge his master. He held no interest in the struggles of the Toran Liberation Army itself.
Still, Kreutz was a powerful ally in battle, wielding an oversized, two-handed sword in battle. Kreutz's strength with the weapon was such that he could crush bones with the power behind his swing, instead of merely killing foes quickly. It is said that fighting with the Liberation Army allowed him to regain his stature as a warrior after having lived in the Dragon Knight's Domain for the past seven years.
Following the defeat of Barbarosa and the fall of the Scarlet Moon Empire, Kreutz simply left the country, his vengeance secured, refusing attempts to bring him into the Republican Army.