What were five things that caused the Persian Empire to fall

Alexander’s strategy of capturing the Persian Mediterranean portsleft them without a navy to threaten Greece and so left him free toconcentrate all his Macedonian and Greek forces against the Persianarmy.

Persian infantry could not stand up to Greek armoured infantry.Alexander’s execution of the Greek mercenaries in the service ofPersia after the battle of Granicus deterred the flow of Greekarmoured infantry to fill this void in the Persian army.

Alexander’s capture of the Persian treasury after the battle ofIssus gave him the funds to pay and feed his cash-strapped army,and keep it intact and augmented for the deciding battle atGaugamela.

Alexander’s integration of armoured infantry-light infantry-cavalryprovided an effective counter-balance to the dominant Persiancavalry.

Alexander organised his campaigns in line with the seasons, makinghis moves at harvest times to overcme the impossible logisticsproblems of providing food and forage across long land distances ina pre-motorised age.