The attention justly paid to the horrors of the war itself should not lead us to ignore the terrible mishandling of the postwar settlement afterwards.
One of the biggest flaws of the post war "peace" was the failure of the Allies to prevent the Bolsheviks from taking over Russia.
Several Allied officials (most notably Churchill in Britain and US Secretary of State Robert Lansing) had better insight on how to handle the peace than others (e.g. - Churchill favoured going relatively easy on Germany and doing more to crush the Bolsheviks). But, overall, it's clear they bungled the peace in many ways, partly because of preventable errors, but partly because of the inherent difficulty of the task. And, while Churchill was unusually insightful when it comes to the peace, he made some serious errors earlier in the conflict.
The mishandling of the peace is also something of an indictment of the decision to go to war in the first place. If handling the war and the peace correctly required special skill and insight not possessed by run of the mill politicians and generals, that strengthens the case against undertaking such a dangerous endeavour in the first place. To adapt a famous line from Madison, very few enlightened statesman were at the helm in 1914-18, and the same is true at most other times.
French President Emmanuel Macron is absolutely right when he says that nationalism was a key cause of the war. It also contributed mightily to the bungling of the peace, and to the rise of illiberal revanchist movements in its wake. Sadly, too many people are inclined to ignore this crucial lesson.
