The Central Powers—Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria—put their armies under a unified command in September 1916. The countries of the Entente—Great Britain, France, and Italy—and the United States did the same only in the spring of 1918. Thus, the first campaigns were fought by military leaders in clumsy, often strained cooperation with one another. German and Austrian generals, along with their British and French counterparts, fought together as best they could. From the start, much of the military sphere was walled off from civilian influence. Bethmann Hollweg had as little to say about the conduct of the German offensive into France as French prime minister Rene Viviani did about the counterstrategy of General Joseph Joffre. In all countries, civilian leaders were discouraged from visiting the front, not only in 1914 but for years thereafter. Only in 1917, when the record of failure and blood had become too obvious to ignore, did leaders like Britain's David Lloyd George and France's Georges Clemenceau try to apply the principle often attributed to Clemenceau that "war is too serious to be left to the generals." And even then, they had only mixed success.