based on the work of Anquetil-Duperron, who had studied Old Persian through the Zoroastrian Avestas in India, and Antoine Isaac Silvestre de Sacy, who had decrypted the monumental Pahlavi inscriptions of the Sassanid kings. Looking at similarities in character sequences, he made the hypothesis that the father of the ruler in one inscription would possibly appear as the first name in the other inscription: the first word in Niebuhr 1 () indeed corresponded to the 6th word in Niebuhr 2. Looking at the length of the character sequences, and comparing with the names and genealogy of the Achaemenid kings as known from the Greeks, also taking into account the fact that the father of one of the rulers in the inscriptions didn't have the attribute "king", he made the correct guess that this could be no other than Darius the Great, his father Hystaspes who was not a king, and his son the famous Xerxes. In Persian history around the time period the inscriptions were expected to be made, there were only two instances where a ruler came to power without being a previous king's son. They were Darius the Great and Cyrus the Great, both of whom became emperor by revolt. The deciding factors between these two choices were the names of their fathers and sons. Darius's father was Hystaspes and his son was Xerxes, while Cyrus' father was Cambyses I and his son was Cambyses II. Within the text, the father and son of the king had different groups of symbols for names so Grotefend assumed that the king must have been Darius. These connections allowed Grotefend to figure out the cuneiform characters that are part of Darius, Darius's father Hystaspes, and Darius's son Xerxes. He equated the letters with the name d-a-r-h-e-u-sh for Darius. This identification was correct, although the actual Persian spelling was da-a-ra-ya-va-u-sha, but this was unknown at the time. Grotefend similarly equated the sequence with kh-sh-h-e-r-sh-e for Xerxes, which again was right, but the actual Old Persian transcription was kha-sha-ya-a-ra-sha-a. Finally, he matched the sequence of the father who was not a king with Hystaspes, but again with the supposed Persian reading of g-o-sh-t-a-s-p, rather than the actual Old Persian vi-i-sha-ta-a-sa-pa. By this method, Grotefend had correctly identified each king in the inscriptions, but his identification of the phonetical value of individual letters was still quite defective, for want of a better understanding of