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.
When we try to understand contemporary events, we often relate them to ones from the past. We do this within the context of our own lives and within the context of human history as a whole. We try to learn from our own mistakes and those of our ancestors.
The issue is that it can be hard to be sure if what is happening now and what happened before are truly comparable. They may be similar in some respects, but we cannot know if they are similar in every meaningful way.
The way we set policy is often flawed. The underrated historian Ernest May argues that we attempt to avoid the mistakes of previous generations by pursuing policies that would have made sense in the past but do not today. May wrote that lawmakers make analogies with history. However, they tend to seize upon the first which comes to mind, without considering differences. They reject disconfirming evidence. In his book, Lessons From the Past, he traces 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.