Weimar–Soviet Alliance, 1920s

At the world economic conference in Italy, [German Foreign Minister Walther] Rathenau charmed and negotiated around the clock, trying everything to press the Allies for some concessions on reparations. He wanted Germany to deal with the West, but France was adamantly opposed—and Rathenau was not the sort of man to let the company collapse just because it was unsuccessful in one market. If the Western democracies would not help Germany, he was determined to "play the Russian card." In a midnight phone call with the Russian delegation, Rathenau arranged a secret meeting in the nearby seaside town of Rapallo. There, he entered into negotiations with none other than Leonid Krasin, the elegant bomb-maker of Baku ... Krasin's terrorist days were over, and he was now helping bolshevism with his smooth negotiating skills and wide knowledge of the oil business. (In fact, his main brief was to sell Baku oil concessions to Western companies on behalf of the new Bolshevik regime ...)

The new special relationship between Germany and Soviet Russia was based on their purely negative common affinity—a hatred for the West and the "victors of Versailles"—and would have terrible unforeseen consequences. Its secret codicils would allow the German Army to illegally rearm and train on Russian territory throughout the twenties and thirties. Tens of thousands of German "work commandos" would come to Russia in 1923 and begin experimenting in the new, still theoretical technique of the blitzkrieg, the idea that small, high-quality, mobile forces backed by airpower could overcome a country before it could react. Under the treaty, the Germans built aircraft outside Moscow and manufactured poison gas in a plant in the Russian provinces. Red and German armies trained their aviators and tank officers together at a series of new schools throughout the Soviet Union. Thus, the armies that would slaughter each other in the 1940s in the most massive mechanized battles in history trained together in the 1920s.

SOURCE: The Orientalist: Solving the Mystery of a Strange and Dangerous Life, by Tom Reiss (Random House, 2005), p. 183

A great many alliances based on "purely negative common affinity" seem to have "terrible unforeseen consequences."