<P> This idea floundered as Europe split into three principal factions in the 1920s and 1930s: liberal democratic states led by the UK and France, communist states led by the Soviet Union, and authoritarian nationalists led by Germany and Italy . The failure of the democratic states to prevent the advance of Nazi Germany ultimately led to the Second World War, which led to a temporary alliance between the UK and the Soviets . The UK did not condemn the Soviet invasion of Poland in 1939, but declared war on Germany . Later they sided with the Soviet Union against Germany after the Axis invasion of the Soviet Union . </P> <P> During the post-Second World War era the Allies split into two blocs, a balance of power emerged in between the Eastern Bloc: affiliated with the Soviet Union and the Socialist nations of Central and Eastern Europe; the Western Bloc: affiliated with the Western democracies, particularly France, the United States, and the United Kingdom, and neutral or non-aligned countries, including the Republic of Ireland, Sweden, Switzerland and Yugoslavia . The majority of the European democratic nations, together with Canada and the US, came together under the military alliance of NATO, which continues to this day and has expanded to other countries in Europe . The first NATO Secretary General, the British Lord Ismay, famously stated the organization's initial goal was "to keep the Russians out, the Americans in, and the Germans down ." </P> <P> From the late 20th century, the four most powerful members of the European Union--the UK, France, Italy and Germany--are referred to as the EU big four . They are major European powers and the only EU countries individually represented as full members of the G7, the G8 and the G20 . The NATO Quint is made up by the United States and the Big Four . </P> <P> The term G4 is especially (although not only) used to describe meeting of the four nations at the leaders' level . In addition, the term EU three (or G - 3) is used to describe the grouping of foreign ministers from France, the UK and Germany during the Iran nuclear talks . On the other hand, the grouping of interior ministers that includes Spain and Poland is known as the G6 . Germany (which has the largest economy in Europe) is often regarded as the EU's economic leader, such as with the ongoing European sovereign debt crisis, whilst France and the United Kingdom (both permanent members of the UNSC) often lead in defence and foreign policy matters, such as the intervention in Libya in 2011, even if the major actor in the attack was Italy . This, to an extent, represents a balancing of leadership power for the Western sphere of the continent . How this balance will change after the Brexit vote in 2016 is still an open matter . </P>

In what ways did the french revolution overturn the balance of power that had existed in europe