If you want to take the current refugee problem in a wider context, we currently have the most refugees worldwide since World War 2. In 2014 there was an estimated 60 million refugees. http://www.unhcr.org/556725e69.html

There was massive displacement during the war, especially in Eastern Europe. Especially Poles and people living within the Soviet Union were fleeing from the oncoming Germans. In the Balkans ethnic cleansing by Ustasha and Cetniks made hundred thousands refugees. After the war about 15 to 20 million Germans were expulsed from Eastern Europe. In the Balkans 200.000 Germans were expulsed, along with other former or percieved foes. In Eastern Europe there were large population exchanges between Ukraine, Poland and Belarus, going into the millions. The people were made to fit the borders. This is followed by a large exodus of Jews from Europe and from the Arab countries to Israel.

The Germans were resettled in Germany and Austria. Most other refugees were resettled in the country matching their ethnicity. The millions of POWs and abducted slave laborers were repatriated to the Soviet Union, while the Soviet Union slowly allowed German POWs to return (over 10 years). Many also fled to the West as they didn't want to live under the now Eastern Bloc/ Warsaw Pact rulership. The United Nations Relief and Rehabilitation Administration was founded in 1943, it should help resettle the many refugees and was providing monetary aid. It is the front runner for todays UNHCR.

The biggest point that is different to today is that the fighting was over, and there was at least a semi-clear destination for the refugees where they belong/ have to go, and the willingness of the various countries to take them in and make them citizens.

Naimark, Norman: Fires of Hatred. Ethnic Cleansing in Twentieth - Century Europe. Cambridge, Harvard University Press, 2001.

there is also, in terms of sheer refugees the Famine Irish in the 1840s.
death and refugees dropped the population of Ireland by about 25%. ireland didn't recover for nearly a century from the loss of labor, economic potential and brainpower. US and Canada benefited.

there's also the massive migration/refugees in the India-Pakistan partition. which ranks up there with the largest movements/transfers of humanity in such a short period - some 14 million people (or more.....)

before that the traditional massive transfers of people are the expulsion of jews from european countries in the middle ages.

In antiquity there was the sheer liquidation of peoples and transference of peoples by the Romans, Assyrians, babylonians and Persians (the persians took the population of an entire greek city and exiled it to afghanistan/bactria where they were forgotten about until "rediscovered" by alexander's army who must have had quite a shock when then walked in speaking greek and got greek spoken back to them)