Original: The expression Istrian exodus or Istrian-Dalmatian exodus is used to indicate the departure of ethnic Italians from Istria, Rijeka, and Dalmatia (present-day Croatia), after World War II.
Simplified: The expression Istrian-Dalmatian exodus is used to indicate the diaspora or forced  migration of ethnic Italians from Istria, Rijeka, and Dalmatia,  after World War II.