War was coming to Europe and the French president, Raymond Poincare, was literally at sea.

Poincare’s trip across the Baltic Sea to St. Petersburg to shore up France’s alliance with Russia in July 1914 cut him off from outside contact for days, adding one more layer of uncertainty to the chaotic, ultimately failed diplomacy that ended in World War I.

A century later, as Russian President Vladimir Putin menaces Ukraine, the world hasn’t banished the risks of the miscommunications, clumsy judgments and botched intelligence that blindsided Europe in 1914, said Max Hastings, a British military historian....