Answer :
The establishment of the independent countries of Czechoslovakia, Hungary and Yugoslavia was the result of (3) World War I. Austria-Hungary had been partitioned into different states which had been largely, but not entirely been constructed along ethnic lines. The details can be found in the Treaty of Trianon and the Treaty of Saint-Germain. Many people were unhappy however with the new borders and fled to different parts where they felt they would fit in better.
