The standard line on why the West has dominated the East traces the cause almost exclusively to technology. The West, for whatever reason, was able to develop modern weaponry before the East and the East simply could not compete. Spears vs. machine guns.
But, of course, the Western development of military technology is itself the expression of the emphasis on rationality that has distinguished it from the East. It is well-known that many of the crucial breakthroughs in military technology - gunpowder, for instance - were first developed in the East. It was the West, however, that typically imagined the military innovations possible with these breakthroughs and exploited them - in the case of gunpowder, with firearms. The West has consistently maintained a lead in military innovation, with the East playing catch-up and never quite getting there.
Neither can the Western dominance be attributed entirely to technology. Hanson uses the example of Cortez who, with a few hundred conquistadors, was able to conquer a sophisticated Mexican empire that numbered in the hundreds of thousands. The crucial difference between Cortez and the Aztecs, Hanson shows, was the way Cortez interpreted Mexican civilization vs the way the Mexicans interpreted Cortez. The Mexicans interpreted Cortez's advent in terms of myth and religion: Was he the white God foretold by their myths? They eventually came to the conclusion that he wasn't, but they never made a genuine attempt beyond that to understand the Spaniards in themselves. Neither did they make efforts to adopt and master Spanish weapons (e.g. swords, armor and cannon) after the superiority of those weapons was made manifest. The Aztecs had access to swords and armor from captured Spaniards as the conflict endured, yet they never made a systematic effort to exploit the captured weapons. Aztec warriors never appeared in captured armor wielding swords, something a Western army would have done as soon as possible when it encountered novel but superior enemy military hardware.
Instead, religion dominated rational considerations of warfare and the Aztecs stuck with their religiously based methods of fighting. Their weapons were designed to stun rather than kill, so that the enemy might be dragged back for ritual human sacrifice. The Aztecs never changed this tactic even when it was obvious that such tactics were particularly unsuited to attacking men wearing chest armor and helmets.
Cortez, on the other hand, made a rapid and systematic evaluation not only of Aztec military technique but also of the political structure of the Aztec empire. He was able to turn the subject peoples of the Empire - who were required, among other things, to provide regular victims to Aztec human sacrifice - against the Aztecs. And after his first attempt to conquer the city failed, Cortez analyzed his failure, came up with a plan based on Aztec vulnerabilities, exploited them, and ultimately conquered.
That's just a brief foray into Hanson's work on cultural history. My real point in this post is to point out that G.K. Chesterton anticipated much of this work way back in 1906, in his August 18 column in the Illustrated London News. (Randomly reading through Chesterton's essays is an exercise that is rarely disappointing, with the occasional discovery of real treasures). What is especially interesting about Chesterton's take on this theme is that he explicitly links it to the Western moral imagination, in contrast to Hanson, who emphasizes what he believes is the amoral character of Western rationality applied to military matters. Here is Chesterton:
Whether or no these details are a little conjectural, the general proposition I suggest is the plainest common-sense. The elements that make Europe upon the whole the most humanitarian civilization are precisely the elements that make it upon the whole the strongest. For the power which makes a man able to entertain a good impulse is the same as that which enables him to make a good gun; it is imagination. It is imagination that makes a man outwit his enemy, and it is imagination that makes him spare his enemy. It is precisely because this picturing of the other man's point of view is in the main a thing in which Christians and Europeans specialize that Christians and Europeans, with all their faults, have carried to such perfection both the arts of peace and war.
Hanson would point out that men like Cortez were hardly humanitarians. One thing the Aztecs did figure out, and pointed out to Cortez's native allies, was that Cortez was not interested in liberating them but in exploiting them. But the natives made the calculation that whatever Cortez was about, it had to be better than serving as a victim in the lethal religious ceremonies in Tenochtitlan.
I don't think Chesterton's point, in any case, was that every Western encounter with the Other had noble intentions. I think it is more that the Western imagination made it possible for Western man to have treat his enemy humanely, because he could imagine him as a human and imagine his point of view. The man who cannot imagine his enemy's point of view doesn't really imagine him as human. In this context Chesterton references another case Hanson treats, that of the conflict between the English and the Zulus:
They [Christians and Europeans] alone have invented machine-guns, and they alone have invented ambulances; they have invented ambulances (strange as it may sound) for the same reason for which they invented machine-guns. Both involve a vivid calculation of remote events. It is precisely because the East, with all its wisdom, is cruel, that the East, with all its wisdom, is weak. And it is precisely because savages are pitiless that they are still - merely savages. If they could imagine their enemy's sufferings they could also imagine his tactics. If Zulus did not cut off the Englishman's head he might really borrow it. For if you do not understand a man you cannot crush him. And if you do understand him, you probably will not.
Well, Chesterton's example of the Zulus is itself a counter-example of that sentiment, since the English certainly did crush the Zulus after the disaster at Isandlwana. But his broader point remains, which is that the Western man, because he can imagine the point of view of his enemy, creates at least the possibility that he will treat him humanely. Aztecs, on capturing Spaniards, would drag them off to be sacrificed, it never occurring to them to do otherwise, even if interrogating them and, possibly, learning from them were they only ways to avoid conquest by the Spaniards. For purely selfish reasons the Aztecs should have treated the Spaniards more humanely.
And I think Hanson would agree with that.