WW I&II, 美国致胜法宝--joined the war at tail end

Time magzine (May 25/2013 edition):
"America Isolated?"
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Historically, America was not eager to jump into the global arena. It entered World War I at the tail end of the war, late enough to avoid the worst bloodshed but still tipping the balance in favor of Britian and France. It entered World War II only after Japan attacked Pearl Harbor. It contained Soviet  aggression in Europe but was careful not to push too far in other places. And when it did, as in Vietnam, it paid a price.
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We have just gone through a decade devoted to a very different idea: that American power must be used actively, pre-emptively and in pursuit of expensive goals beyond the narrow national interest. The result was thousands of American soldiers dead, hundreds of thousands of Iraq civilians dead and millions ethnically cleansed., $2 trillion spent and eroson of American influence and goodwill across the globe.

美国只是鱼公得利，并没有多少值得称颂的将领，主动挑起的战争基本是输的(总体上）.