What alliance opposed the Entente during the First World War?

During the First World War, the Entente was opposed by a bloc of German states – the German Empire and Austria – Hungary. This alliance was strong by Prussia, but weak by the Austro-Hungarian Empire, which gradually fell into decay. Russian troops smashed the Austro-Hungarian troops, many of these troops (Czechs and Slovaks) simply went over to the side of the Russians.
Germany was a stronger adversary, although the Brusilov breakthrough showed that it could be beaten too. In the course of this breakthrough, the Russians advanced into East Prussia with little or no German resistance.