Inexplicably, his wife Ymir chose willingly to aid him in his conquest and atrocities. With the aid of his wife Ymir, Fritz killed countless human lives. For 13 years, the Marleyans kept fighting the Titans and Fritz's army back.
He then moved to a power pursuit of world domination and had Ymir terrorize the rest of the world with the Titans. With the aid of the Power of the Titans, Fritz achieved his dream of ruling the mainland, turning the Marleyan captives into slaves, and founded the Eldian Empire. King Fritz moved to wage war on other cultures, starting with his most bitter enemy, Marley, the greater empire ruling the mainland he lived in at the time. As a "reward", Fritz "allowed" Ymir to bear his children (essentially making her a sex slave), three daughters named Maria, Rose, and Sheena. He used Ymir's power to expand their influence into an empire, building cities and bridges, and crushing the nation of Marley in the process. Upon witnessing her destructive power, Fritz pardoned her of her "crime" in exchange for lending him her power. However, Ymir found her way to an old tree containing a pool and a strange, otherwordly spine-like entity that gave her the power of the Titans. As punishment, Fritz had his men hunt Ymir for sport. One day, when a pig was let loose by one of the slaves, the slave villagers blamed a young girl named Ymir for the crime.
Even then, he was as cruel as he was greedy, enslaving the villages of the land he and his tribe lived in, a mainland mainly controlled by the empire of Marley. Fritz ruled the Eldians over 2,000 years ago when they were still a small tribe.