
The largest empires that the world has ever known are, in order of size, the British, Mongol, Russian, Spanish, Umayyad, Yuan, Qing, French, Abbasid and Portugese empires.
There were a number of other large and notable empires in world history such as the Roman, Ottoman, Greek, Babylonian, Persian and Mughal empires.
The post-World War 1 Soviet empire was massive and powerful and it was followed by the establishment of the post-World War 1 American empire which was equally formidable and which matched it in all ramifications.
The race for supremacy between the two continued after the defeat of Hitler, Nazi Germany and the Axis powers in World War 11 in 1945 and this resulted in the establishment of an unpredictable and frightful bi-polar world, a dangerous cold war and a tense balance of power between them.