At its height the Persian Empire was huge stretching from Macedonia and Thrace to the Indian Subcontinent. Occupation of Upper Mesopotamia. In the 6th century B.C.E. the Persian Empire devastated the lands of Mesopotamia incorporating them into the Empire. These lands formerly belonged to the Median and Neo-Babylonian Empires which themselves in turn took them after destroying the Neo-Assyrian Empire. Adoption of Aramaic. The Achaemenids after capturing Upper Mesopotamia- the land of the Arameans- adopted the Aramaic language as a means of communication,trade and official purposes for the entire Empire. This language was called retrospectively Imperial Aramaic or Official Aramaic and served as a very important means of running and keeping the vast Empire together. Imperial Aramaic was written in the Imperial Aramaic alphabet which dates from the 5th century B.C when Aramaic was adopted as the lingua franca -the language of trade, official documents and communication bet...