Hattusili inherited the throne of Kussara in the 17th century BC, then rapidly defeated his competitors in central Anatolia. Among his conquests was Hattush, which he renamed Hattusha and made his capital. He possibly changed his name to coincide with the name of the city. Hattusha remained the Hittites' political and religious center until the state collapsed. However, it was far north of the Hittite territory center; Hattusili initiated southward expansion into Syria with its enticing fields, which were in contrast to Anatolia's limited agricultural fields amidst its steep valleys and extensive rivers.
Hattusili invaded Yamkhad in northwest Syria, and sacked several cities including Alakh. Yamkhad's capital Aleppo remained un-captured despite several nearby campaigns. Hattusili also campaigned in southwestern Anatolia. However, his large state descended into disarray. Hattusili's sons rebelled against him late in his life, and he was even betrayed by his nephew who was his chosen successor. Thus, on his deathbed, Hattusili appointed his grandson Mursili as his heir. Mursili engaged in a destructive campaign which wiped out major power centers and ushered in a Dark Age.