The Hittites vanished from history and were recovered from a single archive within about a century.
Excavation at Bogazkoy, ancient Hattusa, from the beginning of the twentieth century recovered thousands of clay tablets from the royal archives. Because the Hittites wrote in Mesopotamian cuneiform, the script was already readable when the tablets were found, but the language was not; it was deciphered when it was recognised as Indo-European, which made it the earliest attested language of that family and reorganised the study of the whole group.
What the archive contains shapes what can be said. It is a state archive: treaties, edicts, annals, land grants, and above all ritual and festival texts, prayers and instructions for temple personnel. The Hittites were meticulous about how ceremonies were to be conducted, and the corpus records the machinery of state religion in extraordinary detail.
It also contains texts in several other languages, including Hurrian and Hattic material transmitted by Hittite scribes, so the archive preserves the religion of neighbours who left no archive of their own.
The prayers are the most personal material to survive. Those of Mursili II, composed during a plague, argue with the gods, examine what offence might have caused it, and are among the most direct religious documents from the ancient Near East.
Yazilikaya, the rock sanctuary outside the capital, supplies the visual counterpart: the gods carved in procession, labelled.