Nanda Empire
Alexander the Great invaded Northwestern India and defeated King Porus in the Battle of the Hydaspes River. The same region was soon re conquered by Chandragupta Maurya after defeating the Macedonians and Seleucids. He also went on to conquer the Nanda Empire and unify Northern India. Most of Southern Asia was unified under his grandson Ashoka the Great after the Kalinga War, though the empire collapsed not long after his reign.