Which countries fought on the side of the Entente, and which on the side of the Fourth Alliance?

At the initial stage of the First World War, the Entente included Russia, France, England, as well as Serbia and Montenegro. At the end of August, Japan joined them in order to knock the Germans out of their sphere of influence in China (Qingdao). And also Belgium, which was suddenly attacked by Germany. In 1915-1918 the Entente was joined by Italy, Romania, Portugal, Greece, USA, Thailand, as well as a number of countries of the Western Hemisphere, for example, Uruguay, Ecuador and Cuba.

Far fewer countries fought on the side of Germany, for example, Austria-Hungary, the Ottoman Empire, Bulgaria. Romania fought on the side of the central powers at the turn of 1917-1918, then again deserted to the Entente.