The Versailles settlement of 1919 was deeply flawed. Comparisons with the Vienna settlement of 1815 are to the point. After twenty-two years of war rooted in French attempts to dominate Europe the victorious powers (Britain, Russia, Austria and Prussia) imposed a lenient peace on France but backed that peace with a defensive military alliance of the victors against any French attempt at territorial revision. In 1919 the victors imposed a harsher peace on Germany but failed to guarantee it by military force. Unsurprisingly, the Vienna settlement in its key points lasted for ninety-nine years, the Versailles settlement for twenty. Without American intervention the Western allies would not have won the First World War.
When the vagaries of American domestic politics led the USA to withdraw into isolation after 1919 the European order created by their intervention was threatened. With Britain also staging one of its periodic retreats from Europe after 1919, the French were left with the burden of sustaining the territorial order created at Versailles more or less on their own. Much weaker than Germany in both industry and population, France had no chance of bearing this burden in the longer run.
The First World War’s causes lay mostly in Eastern Europe. Above all this meant the crisis of the Ottoman and Austrian empires, and the German fear of growing Russian power that impelled Berlin to start a European war in 1914 at a time when it was still confident of victory. Ironically, a war that began as a struggle between the Russians and Germans to dominate east-central Europe, ended in the defeat and disintegration of all three empires (Romanov, Habsburg, Hohenzollern).
The huge area of the former Austrian empire became a geopolitical vacuum, its instability enhanced by the conflicts between ethno-national groups that are the usual result of an empire’s disintegration. The Versailles settlement was made against Russia and Germany, and without their participation. Although temporarily flattened in 1919 by defeat and revolution, the Germans and Russians remained potentially much the two most powerful communities in Europe. A peace settlement that ignored their interests and wishes was unlikely to last once their latent power was restored, which happened in the 1930s.
Faced with resurgent German power directed by an openly expansionist leadership, the safest response would have been the re-creation of the Franco-Russian-British alliance created before 1914. Had Russia stood among the victor powers in 1919 and participated in the peace settlement this would probably have happened. Had even the Franco-Russian alliance survived then Nazism would have been stopped in its tracks. But creating an alliance to deter Hitler and defend the Versailles order between Soviet Russia and liberal-capitalist France and Britain was very difficult. Mutual trust was impossible. Interests and ideologies were too divergent. One of the tragedies of twentieth-century Russian history was that because of the implosion of Russian power in 1917, the Russian people (and the rest of Europe) had to fight the First World War twice. With instability spreading across much of Eastern Europe and the Middle East, we are today in many ways back where we were in 1919: contemplating the chaos left behind by the collapse of the Russian, Austrian, Ottoman and German empires.