Suppiluliuma married a sister to the Hayasan king Hukkana, and his daughter Muwatti to Maskhuiluwa of the Arzawan state Mira. He also married a Babylonian princess and retook Arzawan territory as far as Hapalla. His most permanent victory was against the Mitanni kingdom, which he reduced to a client state under his son-in-law Shattiwazza. He was also a master builder of large stone structures decorated with stone reliefs. It was during his reign that concepts of the sacred nature of royal leaders developed.