What is "piyassili"

Piyassili (also transliterated as Piyaššili; died ca. 1315 BC), also known as Sarri-Kusuh (or Šarri-Kušuḫ), was a Hittite prince and a middle son of King Suppiluliuma I—younger than the heir Arnuwanda II, but older than the eventual successor Mursili II and probably older than the ill-fated Zannanza too. After Suppiluliuma concluded a treaty with Sattiwazza, son of King Tusratta of Mitanni, and married one of his daughters to him, Piyassili led a Hittite army that put Sattiwazza on the throne of Hanigalbat. According to Hittite sources, Piyassili and Sattiwazza crossed the Euphrates at Carchemish, then marched against Irridu, already in Hurrian territory. After having reduced Irridu and Harran, they continued east towards to Wassukanni and perhaps conquered the capital Taite as well.