I've read my share of books about Genghis Khan (including the recent 'Genghis Khan and the Making of the Modern World' by Jack Weatherford) and he is certanily a fascinating figure, but GK is probably even more of a mysterious and unknown figure than Alexander is when it comes to facts. Compared to the rather detailed info we have about the structure of the Macedonian army and Alexander's campaigns, the bits of info on GK's army and tactics are scattered and scanty at best. The Mongols in GK's time and afterwards were illiterates, so there simply isn't much info that survived on paper, only word of mouth. GK's army had no infantry to speak of. GK himself wasn't physically courageous and despised the sight of blood, as did most Mongols. They were almost entirely about archers on cavalry. And yet they wiped out opponents stretching from Korea to the borders of Austria. It's hard to make sense of it and my research into how they did it doesn't supply satisfactory info.
In any case, what GK accomplished and the effects of the Mongol empire can't be denied. Still, I can't help but roll my eyes when reading books and stuff on the web that seem to exaggerate what GK accomplished and that it is the "greatest" empire of all time. Mainly, they talk about the sheer size and how quickly it was conquered. By land mass, it does indeed dwarf Alexander's empire or the Roman. Okay, good enough. But then these GK fanboys would go on about how the Mongol army would have destroyed Alexander's army or the Roman legions.

I don't know how many of you have really looked into the other great conquerors and military leaders of history. Besides Alexander, I've done a good deal of research on Caesar, Napoleon, and quite a lot on Genghis Khan. I haven't been able to muster too much interest in Napoleon yet but I figure that will happen soon enough. I'm really not keen on the fighting techniques of that era (including the American Revolutionary War), but I do want to learn more about that whole era because it was a fascinating time that dramatically and profoundly shaped the Western world we now live in. So what are your thoughts when you compare Alexander to the likes of Caesar, Genghis Khan and Napoleon or other great military commanders like Hannibal? BTW, here's a list of the 100 most "influential" military leaders of all time:
http://www.adherents.com/people/100_mil ... ilitary100
http://www.carpenoctem.tv/military/intro.html