Is there a precedent for a country attacking another due to unverified information and finding out later they were wrong? And what was the international response?
Narrowing scope: An event that was misunderstood by the attacking side that they later admitted was wrong (specifically of their own accord), but not as part of the post-war surrender process. (i.e. the US striking Syria without declaring war because of, yet unverified, reports of the government using chemical weapons on its own citizens)
Country A believes Country B's leader insulted theirs, country A launches missiles/drops bombs/invades territory, short time later Country A realizes that the insult hadn't happened, withdraws and apologizes.
Like the Ems Dispatch incident where a bad translation heightened tensions between France and Germany and may have been a factor in the Franco-Prussian war.