Germany and Russia signed the secret Reinsurance Treaty that ensured they would each remain neutral if the other went to war with a third European power.
Germany, Russia and Austria-Hungary had entered into a second Three Emperors’ Alliance in 1881. Like the one before it, the agreement was designed by the German Chancellor, Otto von Bismarck, to isolate France from potential allies and avoid rivalry between his two neighbours over territory in the Balkans.
Continuing tensions between Austria-Hungary and Russia over this region led to the agreement’s collapse in 1887 and forced Bismarck to find another way to maintain French diplomatic isolation.
Germany had already formed the Dual Alliance with Austria-Hungary in 1879, so the Reinsurance Treaty was created to ensure Russia continued to side with Germany. In return Germany agreed to a Russian sphere of influence in Bulgaria and the Black Sea.
By the time the treaty came up for renewal in 1890, Wilhelm II had become Kaiser of Germany. He insisted that Bismarck resign the Chancellorship in March that year, and argued that his personal relationship with Tsar Alexander III would be enough to avoid any future problems with Russia. Bismarck’s successor Leo von Caprivi was also unwilling to seek a renewal of the Reinsurance Treaty, meaning that it lapsed.
Without the treaty to tie St Petersburg to Berlin, the Russian government began to forge closer relations with France. France’s improving diplomatic situation was formalised in the Franco-Russian Alliance of 1892. This opened up Germany to the possibility of a war on two fronts, making the failure of the Reinsurance Treaty a contributing factor to the outbreak of the First World War.