The letters were written in Akkadian, the diplomatic lingua franca of the day used in international relations,
Akkadian, known from cuneiform inscriptions, is the oldest Semitic language for which records exist. It was used in Mesopotamia from about 3500 BC; two dialects, Assyrian and Babylonian, were widely spoken in the Middle East for the next 2,000 years, and the Babylonian form functioned as a lingua franca until replaced by Aramaic around the 6th century BC.
