Ascherson in his book Black Sea mentions that the European portion of the Inner Eurasian trade routes, at least by the evidence he has presented, and those from High Medieval Europe who traveled it like Rubruck, Clavijo and others, seems to have begun in the Crimea, passed north of the Caspian, across the Volga, through the Kipchak Steppe into Kwarazm, into Trans-Oxiana and then into China or down through Afghanistan into India. This does seem to be where most of the trade to Europe traveled. If so, which ports were more important? The Crimean ports of the Italians? Or the Levantine ports of the Franks? What would have happened had the Crusader States lasted an extra two hundred years? Or the Byzantine Empire held an extra hundred years–which might well have been a real possibility had it not been for the Fourth Crusade? What would have happened had Timur not wrecked the Kwarazmian trade routes to the north as Knobloch, in his book Monuments of Central Asia, implies?