Cheezy the Wiz
Socialist In A Hurry
Only by people indoctrinated by the Renaissance.

Here's an epic screwup, which I already mentioned in the "unexpected wars" thread. The ruler of Khwarazem, a Muhummad II, had sent envoys to make a pact with Genghis Khan. He basically stipulated that Genghis was the rightful ruler of the Eastern half of the world, and that he was the ruler of the Western half of the world. Rather than being enemies and competing for it all, he proposed that they work together for mutual trade and benefit. Genghis seemed to agree, or at least had no immediate plans for an invasion of of SW Asia, and so the two were at peace. However, Muhummad suspected, perhaps rightfully so, that Mongol caravans passing through his lands were acting as spies. When one of his governors in Transoxiana took a large caravan sent by the Khan himself, supposedly as a gesture of goodwill, into custody, Muhummad ordered them slaughtered. One of the camel herders escaped, however, and returned to tell the Khan of the massacre. By this harsh show of force, Muhummad hoped to show the Khan he meant business, and to leave him the hell alone. Interestingly, the Khan responded rather weakly, and sent three more emissaries to Urganj. Muhummad had one killed, and shaved the beards of the other two, who then returned to their master in shame. Genghis thus felt compelled to right these wrongs, and began assembling one of the largest armies in history for an invasion of Kara Kitai and Khwarazem. This army then continued on to Afghanistan, India, Persia, and up around the Caucasus, where it participated in the invasion west, into Europe, with further armies coming East.
Great job Muhummad II.
