Will there be another war between Israel and Hezbollah? Over the past few months I’ve put this question to many experienced commentators in Lebanon, and most of them doubt that there will be a conflict any time soon. The most common reason they give for their optimism is that starting a war is not in the interest of either party. Israel risks greater political isolation if it attacks Lebanon, while Hezbollah handsomely benefits financially from the calm.

This optimism is dangerously naive. States often start wars even when it is not in their interest to do so. Experts in international relations refer to this phenomenon as “the war puzzle.” States led by rational decision-makers should never fight, the argument goes, because both sides could avoid the costs and risks of war by negotiating a prewar bargain reflecting their relative power. That is, both sides could obtain the same result they would by going to war, but without incurring the high costs that war entails – just as the males of many other species settle their disputes without actually fighting.

One explanation of the war puzzle may be that human groups, whether bands of hunter-gatherers or modern nation-states, tend to overestimate their relative power. However, that is not strictly necessary. A country that knows itself to be weaker may nevertheless choose to fight in an attempt to force an advantageous settlement, or because it prefers to die on its feet rather than live on its knees.

But this is more the exception than the rule. When two states go to war, typically both of them think that they have a good chance of winning. As the British statesman Winston Churchill once observed, “However sure you are that you can easily win ... there would not be a war if the other man did not also think he had a chance.”

Many wars may be the result, then, not of rational calculation, but of overconfidence and miscalculation. But where does this overconfidence come from? The British political scientist Dominic Johnson thinks that the tendency to overestimate our chances of winning fights evolved because it was beneficial to our ancestors. Natural selection, he argues, favored overconfidence in early humans in the small-scale, low-tech skirmishes that characterized human combat for most of our evolutionary history. One reason is that it could have helped make fighters more tenacious and aggressive.

The same overconfidence is probably more difficult to adapt in today’s large-scale, high-tech conflicts. Yet modern warfare is far too recent in evolutionary terms for natural selection to have scaled back human confidence accordingly. Like our preference for sweet foods, which was useful when it motivated our ancestors to seek out nutritious fruit but can lead to obesity in today’s world of fast-food restaurants and convenience stores, overconfidence may be an evolutionary leftover that no longer necessarily serves humans well.

Unlike bands of hunter-gatherers, modern armies are characterized by extended chains of command. Johnson suggests that the pros and cons of overconfidence may vary at different levels in this hierarchy. For soldiers at the sharp end, overconfidence may still be as advantageous today as it was for our hunter-gatherer ancestors. However, for high-ranking officers in charge of strategic planning far from the battlefield, overconfidence may lead to the misallocation of resources without any compensating benefit.

At the highest levels of political power, the situation may be more akin to that of the soldiers on the ground than to the officer corps. Displays of resolve and bluffing between national leaders, Johnson notes, are quintessential elements of international politics. Genuine conviction and confidence, over and above conscious strategizing, are signaled in public speeches, negotiations, political bargaining, diplomacy, alliances, treaties, the development and deployment of military power, and even parliamentary infighting.

A certain amount of overconfidence may, therefore, be just as useful for the political leadership as it is for soldiers on the battlefield. But it also cuts both ways. Resolve and bluffs may at times bolster national security, but at other times they may drive countries into wars that they would have been better off avoiding. This last danger is precisely what the optimists neglect when estimating the chances of a conflict between Israel and Hezbollah.

Israel is deluded if it thinks that it can inflict a crushing military defeat on Hezbollah. Likewise, Hezbollah is fooling itself if it thinks that it can achieve more than a stalemate in any future confrontation with Israel. Perhaps this is just posturing. The danger is when political leaders on both.