The Treaty of Versailles and subsequent agreements recognized the creation of nine new countries from the remains of the Austrian, Russian, and German Empires: Finland, Lithuania, Lativia, and Estonia from Russia; Czechoslovakia, Yugoslavia, Austria, and Hungary from the former Austrian Empire; and, Poland, which included parts of the pre-war German, Austrian, and Russian Empires. Switzerland, Romania, Bulgaria, and Albania existed before WWI, while Slovakia was created by the dissolution of Czechoslovakia in 1993.

The Balfour Declaration was issued in 1917 by the British Foreign Secretary asserting British support for the creation of a Jewish state in Palestine, which had been part of the Ottoman Empire. This declaration was an attempt by the British to weaken the support of German and Austrian Jews for their governments' pursuit of the war. This proposal contradicted a promise made to the Sharif of Mecca (via the Hussein-McMahon Correspondence of 1915) that the British would support the creation of an Arab state (that included the territory of Palestine) if the Arab population of the Ottoman Empire would revolt against that state. In fact, both promises contradicted a secret plan agreed between Britain and France in 1916 (the Sykes-Picot Agreement) to split and occupy the Arab territories of the Ottoman Empire after the war.

After World War II, the Cold War between the communist USSR and the rest of the western, capitalist nations erupted in Berlin. Berlin was located in Soviet controlled East Germany, but was also partitioned into four sections controlled by France, the UK, the US, and the USSR. Between June 1948 and May 1949, the Soviet Union blockaded access to the Western, non-Soviet portions of Berlin in the hopes of the entire city eventually coming under their sphere of influence. In response, the capitalist allies conducted over 200,000 flights, dropping food and other necessities into the blockaded areas of western Berlin. This was successful in maintaining West Berlin free from the communist block, but also led to the erection of the Berlin Wall in the 1960s.  

The Bretton Woods System was the first fully negotiated international system that governed monetary policy amongst different countries. It required each participating nation to adopt a monetary system, and maintain an exchange rate that was pegged to the value of gold and thus indirectly the value of the U.S. dollar. This free convertibility of currency allowed for increased free trade between Allied nations after WWII. This allowed for investment and aid in rebuilding Germany and Japan, as well as the subsequent boom in international trade after the war. It was ultimately ended in 1971 "Nixon Shock", after the U.S. decided to no longer tie the value of the dollar to gold and also no longer guaranteed the convertibility of U.S. dollars to gold - essentially making the dollar a fiat currency. 

Shortly after the end of World War II, tensions between the United States and the Soviet Union quickly flared. In order to swiftly build a sphere of influence in Western Europe and prevent the Soviets from expanding their own, the United States passed the Marshall Plan. A massive influx of capital, the Marshall Plan went a long way to rebuilding both the economy and infrastructure of Europe's war-torn nations. 

The Soviet Union was threatened by the creation of NATO, so they made their own.  Established in 1955, the Warsaw Pact made for military and economic cooperation between its member nations. However, while ostensibly created as a counterbalance to NATO and the United States, the two organizations never had a direct confrontation. The Warsaw Pact was dissolved shortly before the fall of the Soviet Union in 1991. 

After World War II, Berlin was split into four zones- American, English, French and Soviet. As Cold War tensions grew more rampant, it became harder and harder to move to and from Soviet-controlled Berlin. This state of affairs finally culminated in the building of the infamous Berlin Wall, which would stand until 1991. 

The Polish-Soviet War took place between 1919 and 1921, ending in a bloody Soviet loss. Inspired to "spread the Revolution", Soviet Russian forces attacked across Eastern Europe, with the ultimate goal of annexing Poland. Important to note is that it was Soviet Russians, not Soviets who attacked. At the time, only Russia, not all of what would become the Soviet Union, was under Soviet control. These non-Russian areas (the Central Asian Republics for example) would only be under Soviet control later on. 

The USSR and a handful of her satellite states refused Marshal Plan aid, seeing it as a ploy on the part of the United States to expand its influence at the expense of the USSR as well as an aggressive move on the part of capitalist powers to undermine the legitimacy of communist power in Europe.

The Sykes-Picot Agreement, signed in 1916 and enacted after the end of WWI, carved up former Ottoman lands into "mandates", artificially defined areas to be watched over by British and French forces. Though there have been subsequent border changes of varying degrees, the borders drawn in the agreement are, by and large, the borders accepted by most contemporary Middle Eastern states.