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Hanson argues that the military dominance of the West can be attributed to the idea of dissent, consensual government, and individualism. Hanson rejects racial explanations for this military preeminence, the dominance of technology and disagrees with environmental or geographical explanations such as the thesis advanced by Jared Diamond in Guns, Germs and Steel.
According to Hanson, Western values such as freedom, rationalism, and open dissent are a particulary lethal mix as the West has engaged in warfare. Even when non-Western societies win the occasional victory when warring against the West, it is only a temporary setback and the non-Western culture is dependent of Western tactics, technology, and has no inclination to fight to totally vanquish their foe. Therefore, the "Western way of war" will ultimately prevail. Hanson is careful to point out that Western warfare is not necessarily more (or less) moral than war as practiced by other cultures; but his argument posits that the "Western way of war" is unequalled in its devastation and decisiveness.
Nine battles illustrate a particular aspect of Western culture that Hanson believes contributes to the dominance of Western warfare: the Battle of Salamis 480 BCE, where the Greeks fought as a "free citizens," the Battle of Gaugamela 331 BCE in the decisive battle of annihilation, the Battle of Cannae 216 BCE emphasizing civic militarism, the Battle of Tours/Poitiers 732 CE and the concentration of infantry, the Battle of Tenochtitlan 1521 CE where technology and reason prevailed, the Battle of Lepanto 1571 or a victory for capitalism, the Battle of Rorke's Drift 1879 where British discipline held sway, the Battle of Midway 1942 demonstrating individualism, and the Tet Offensive 1968 where American dissent rose to the fore.
One of the biggest surprises of the book is the numerical superiority of the Americans during Tet. The Americans felt as though they lost though Hanson points out that the Vietcong were really decimated in the American counter-offensive. The work is an important corrective to the current American penchant for defeatism. Not surprisingly then, Hanson argues that the current American conflicts against insurgency and terrorism can result in an American victory.