I have been criticized, and indeed mocked, for suggesting that personal pique could play a major role in international affairs - in particular, Netanyahu's repeated disrespecting of the American President.
Margaret MacMillan, in her examination of the causes of World War I, pays some attention to the human factors which led to the gradual deterioration of relations between Britain and Germany, including rude and angry letters between their respective sovereigns, Kaiser Wilhelm II and Queen Victoria (his grandmother). Official quarrels of little import became magnified by annoyed public opinion.
Samoa, for example, was a crisis that need not have happened because no great national interests were at stake. Yet it proved unnecessarily difficult to resolve because of public agitation, especially in Germany. “For even though the great majority of our pothouse politicians did not know whether Samoa was a fish or a fowl or a foreign queen,” said Eckardstein, “they shouted all the more loudly that, whatever else it was, it was German and must remain forever German.” 18 The German press suddenly discovered Samoa to be essential for national prestige and security.
Macmillan, Margaret (2013-10-29). The War That Ended Peace: The Road to 1914 (Kindle Locations 1410-1416). Random House Publishing Group. Kindle Edition.
The Kaiser's tendency toward rude and childish practical jokes:
Indeed, the King of Bulgaria, a country which Germany hoped to make an ally of, once left Berlin “white-hot with hatred” after the Kaiser smacked him on the bottom in public.
Macmillan, Margaret (2013-10-29). The War That Ended Peace: The Road to 1914 (Kindle Locations 1500-1502). Random House Publishing Group. Kindle Edition.