hISTORY eNDS EVERYWHERE:

Afghanistan, if anything, was less similar to Vietnam than Vietnam was to Korea, in terms of politics, culture, religion, geographical context, and other elements important to military and diplomatic affairs. The world of the 2010s and 2020s was far more unlike that of the 1960s and 1970s than the world of the 1960s and 1970s was unlike that of the 1950s. So there is no prima facie reason the lessons of Vietnam should be more pertinent to Afghanistan than the lessons of Korea were to Vietnam.

All this is to offer a reminder that predicting the future is hard. Or, rather, it's hard to get right, on a consistent and timely basis. Most of Lyndon Johnson's advisers in 1965 told him the war in Vietnam was winnable; the chief dissenter, George Ball, turned out to be correct, but in 1965 he wasn't obviously more intelligent or better informed than Robert McNamara, Dean Rusk and the other hawks. South Korea's turnaround was a long time coming; many pessimists thought it might never come.

Predicting events in world affairs is like predicting the weather. Meteorologists don't usually say tomorrow will bring rain or it won't; they offer a probability. If they're very confident, they might forecast a 90 percent chance of rain at a given hour; if it could go either way, they'll put the chance at 50 percent. And they base their forecasts on how similar conditions today are to the days in the past that were or weren't followed by rainy days. Then they leave it to you to decide whether to take an umbrella.

Intelligence analysts often do something like this. But their shadings of confidence can get washed out in the decision process, in which leaders typically have to make binary yes-or-no choices, and often feel obliged to defend their choices with more confidence than they actually feel. Outsiders are left to wring their hands afterward and ask why no one saw this or that coming. The fact is that people did see it coming, but only on a scale of probability.   

So go ahead and second-guess the people who have to make the decisions. But remember the advantage you have over them: you know whether it actually rained. And, anyway, you're probably sitting inside where it's dry.  

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