The most diverse people who were united?

During the wars and several other events in the history, there were certainly some different people with different races, languages, religions and etc who were united, however I'm myself a Persian and the ancient Persian army, as mentioned by Greek historians, was one of the most diverse union of people from three different continents, but I prefer an alliance of different peoples against a superpower, like what happened in the first century BC in Parthia against the Roman empire.