The tendency to relate contemporary events to earlier events as a guide to understanding is a powerful one. The difficulty, of course, is in being certain that two situations are truly comparable. Because they are similar in some respects does not assure us that they are similar in all respects.
We all know the way in which we set policy is flawed. Ernest May, someone you've likely never heard of, argues that in attempting to avoid the mistakes of the previous generations we pursue policies that would have been the most appropriate from a historical context. May argues that lawmakers mentally resort to analogies and tend to seize upon the first analogy that comes to mind without seeking evidence that would disprove their assumptions (like, say, highlighting differences between this event and the previous one before drawing conclusions?). After publicizing policy ambitions our politicians, like anyone, are likely to reject evidence that does not confirm their conclusions
Ernest May, in his book Lessons of the past, traced the impact of historical analogy on US foreign policy.
He found that because of reasoning by analogy, US policymakers tend to be one generation behind, determined to avoid the mistakes of the previous generation. They pursue the policies that would have been most appropriate in the historical situation but are not necessarily well adapted to the current one.
Policymakers in the 1930s, for instance, viewed the international situation as analogous to that before World War I. Consequently, they followed a policy of isolation that would have been appropriate for preventing American involvement in the first World War but failed to prevent the second. Communist aggression after World War II was seen as analogous to Nazi aggression, leading to a policy of containment that could have prevented World War II.
The Vietnam analogy had been used repeatedly over many years to argue against an activist US foreign policy. For example, some used the Vietnam analogy to argue against US participation in the Gulf War–a flawed analogy because the operating terrain over which battles were fought was completely different in Kuwait/Iraq and much more in our favor there as compared with Vietnam.
May argues that policymakers often perceive problems in terms of analogies with the past, but that they ordinarily use history badly: When resorting to an analogy, they tend to seize upon the first that comes to mind. They do not research more widely. Nor do they pause to analyze the case, test its fitness, or even ask in what ways it might be misleading.