Dear, in Army we do discuss various good battles fought, tactics/weapons/leadership traits displayed, however, Alexander had less importance in todays warfare, Also neither I am in teaching profession nor have some library/time to put few lines from books and you will agree that in this old age and without in touch to such material, it is difficult to write some thing and specially when people ask proof for every thing whether to understand or to collect material for future self use.However, For Army, his move with lightning speed and surprised his enemies, was an important contribution of his, At the age of 22, he started his project of expansion, with in ten years he conquered Asia minor, Syria, Egypt, Mesopotamia and Iran. H e reached India in 327BC, HE WAS WELCOMED BY AMBHI, KING OF TAXILA, WITH THE HELP OF AMBHI HIS ARMY MARCHED FORWARD TO CROSS hYDASPES9 JHELUM, to his surprise he found the mighty Army of PORUS, A FIERCE BATTLE FOLLOWED, PORUS ARMY FOUGHT WELL BUT unfortunately Porus got wounded and got captured, Here Alexander behaved like a good soldier and porus was let free with his kingdom, From here he had to return back due to to reasons, a) he and his people realized the strength and fighting spirit of Indians and also realized that it would be very difficult to move against Nandas. b) his soldiers were tired, were away from their families for last 10 years, so very reluctantly he returned back, Further you can analyses and let us know your expert views