I don't think anyone doubts that Alexander was awesome. But the question is who was better, Qin or Alexander. Napoleon was also awesome until he met the russians.
Not to get off topic but Napoleon was awesome until his army encountered the
RUSSIAN WINTER and the combined opposing armies of Europe, be they British, German or Russian were outmatched until the Russian Winter killed off more troops in a few months then then Napoleon's army normally lost in years worth of hard fighting.
Then lest we think the Russian Winter was just a fluke Adolf Hitler pretty played Napoleon's part over again doing well until his army moved into conditions far colder then any German army had ever operated in.
Russia has 2 great generals in history, general January and general February. Conquering Russia means starting in the spring and ending before fall. The Russians themselves deserve some credit of course, but its probable they could not have withstood more elite forces without the intervention of some of the cruelest seasonal weather to be found anywhere on Earth.
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As for weather however I do wonder how bad the weather would be to Alexanders army in its most likely entry point into Chinese territory (The extreme southwest) I am not familiar with the lay of the land in that area but I suppose it could be miles and miles of barren grassland requiring long long supply lines, until the Alexandrian army could begin foraging Chinese farmland.
Anybody have any idea what the environmental conditions would have been like along Alexanders most likely (theoretical) paths of invasion of the Qin?