The Nanda empire was much bigger than its predecessors, and they were ruling at the time Alexander the Great launched his campaign into India.
The territory that the Nanda’s controlled is shown in the map below, and after defeating Porus or Purushottum on the river Jhelum, Alexander’s army would have to contend with the Nanda’s next.
The common sources about Nandas say that they were not very popular rulers, and also that they declined King Porus’ plea to help fight Alexander the Great. King Taxiles or Ambhi of Taxila had already surrendered to Alexander the Great, and Porus decided to fight him on his own and although defeated; handed him the heaviest losses yet.
The Battle of Hydaspes between Alexander and Porus is one of tactical genius by Alexander the Great, and there is a great documentary about it that I am embedding below.
This is the last battle of Alexander the Great because his soldiers mutinied at this point, and would no longer fight. According to Greek sources the Nanda army under ruler Dhana Nanda consisted or 3,000 to 6,000 war elephants, and that was simply too much for the Greeks to contend with.
King Dhana Nanda inherited the vast empire of his father. The army of Emperor Dhana Nanda consisted of a large number of cavalry, infantry, chariots and elephants. As described by Diodorus and Quintus Curtius Rufus, the army consisted of 200,000 infantry, 20,000 cavalry, 2,000 war chariots and 3,000 war elephants. According to Plutarch however, it was even larger, numbering 200,000 infantry, 80,000 cavalry, 8,000 war chariots, and 6,000 war elephants.
This army however would not be enough to stop the next great empire – the Maurya empire to wipe them out.