Wikipedia on Serb Diaspora

There are currently 3.5 million Serbs in diaspora throughout the world (those that are not constitutional peoples; like in Serbia, Montenegro and Bosnia and Herzegovina in this case). The Serb diaspora (commonly known as the Serbian diaspora) was the consequence of either voluntary departure, coercion and/or forced migrations or expulsions that occurred in six big waves:

To the west and north, caused mostly by the Ottoman Turks.

To the east (Czechoslovakia, Russia, Ukraine and across the former USSR from World War I and World War II, to until the fall of Communism in Eastern Europe by the early 1990's).

To the USA for economic reasons, but Serbians also migrated to Canada, Australia, New Zealand, and South America.

During wartime, particularly World War II and post-war political migration, predominantly into overseas countries (large waves of Serbians and other Yugoslavians into the USA, Great Britain, Canada, Australia and New Zealand).

Going abroad for temporary work as "guest workers" and "resident aliens" who stayed in their new homelands during the turbulent 1960s and 1970s (to Austria, Belgium, Denmark, France, Germany, Greece, Italy, the Netherlands, Portugal, Spain, Sweden and the United Kingdom), however some Serbians returned to Yugoslavia in the 1980's.

Escaping from the uncertain situation (1991-1995) caused by the dissolution of Yugoslavia, the renewal of vicious ethnic conflicts and civil war, as well as by the disastrous economic crises, which largely affected the educated or skilled labor forces (i.e. "brain drain"), increasingly migrated to Western Europe, North America and Australia/New Zealand.

The existence of the centuries-old Serb or Serbian diaspora in countries such as Austria, Czech Republic, Greece, Hungary, Italy, Romania, Russia, Poland, Slovakia, Turkey and Ukraine, is the result of historical circumstances – the migrations to the North and the East, due to the Turkish conquests of the Balkans and as a result of politics, especially when the Communist Party came into power, but even more when the communist state of Yugoslavia collapsed into inter-ethnic conflict, resulting in mass expulsions of people from certain regions as refugees of war. Although some members of the Serbian diaspora do not speak the Serbian language nor observe Christianity (some Serbians are Jews, Slavic Muslims, Protestants, Roman Catholics, Eastern Rite Catholics, and atheists who don't practice religion) or members of the overseas dioceses of the Serbian Orthodox Church, they are still traditionally regarded as Serbs or Serbians other than Yugoslavians or Yugoslavs.