While India largely remained at the food-gathering stage, the more advanced Indus valley gravitated once again towards the markets of the rich slav-owning societies of western Asia, Persia and Mesopotamia. In 513 BC, Darius I annexed Indus to the umpire of the Great Cyrus. The famous politician and a prominent lawyer Mr Aitzaz Ahsan, writes about the invasion of Alexander and his battle with Porus, in his book "The Indus Saga and The Making of Pakistan" in the following words: A the time of the Greek invasion Indus had for some time been a part of the Achaemenid Empire of Iran, and thus a part of the central Asian politico-cultural system. This is a huge mound, spread over an area of at least 50 acres. Just 5 kilometers to the northeast of Mandi Bahauddin. It is known to be the likely place of the capital of Raja Porus. One of those is located beside Lakhne Wala, a village near Mandi Bahauddin. Punjab as a whole has hundreds of mounds, which are sites of ancient cities and settlements that have not been explored or studied properly. Though some people believe that Mong, a village 5 kilometers north of Mandi Bahauddin is the place, where this battle was fought. But that city has not been discovered or located as yet. Alexander constructed a city, Nicaea, at the site of the battle. This battle was fought somewhere near the eastern banks of the river Jhelum, hence called Battle of Hydaspes (Greek name for Jhelum). After conquering the Gandhara region, Alexander entered the plains of Punjab, where Raja Porus was ready to give him a tough fight. At the time of the invasion of Alexander the Great, Jech Doab was ruled by Raja Porus. These Doabs since the dawn of civilization, have been centres of important cultural and political activities.