It is known from six references in 13th century BC Hittite sources, including:
- the Manapa-Tarhunta letter (ca. 1310-1280 BC); which places it beyond the Seha river;
- the Alaksandu treaty (ca. 1280 BC), between Alaksandu of Wilusa and Muwatalli II of Hatti;
- the Tawagalawa letter (ca. 1250 BC), addressed to the king of the Ahhiyawa by Hattusili III, mentioning a military conflict over Wilusa;
- the Milawata letter (late 13th century BC), believed to be written by Tudhaliya IV of Hatti, discussing the reinstallation of Walmu as king of Wilusa;
It is often identified with Troy VIIa in archaeology (destroyed in ca. 1190 BC), and with legendary Troy of the Greek Trojan War cycle (according to the chronology of Saint Jerome dated to the 1180s BC). In terms of etymology, Ilios ~ Ilion, a Greek name for Troy, comes from Wilusa.