Hitler exploited irredentism brilliantly in his annexation campaign. First was the re-militarization of the Rhineland. Hard to argue with that one because it actually was inside Germany.
Second was the anschluss with Austria. Again, hard to argue with. They're all Germans, anyway, right, and if the Austrians want to join up . . .
Then came the Sudetenland. Those Germans had never been German citizens - they were holdovers from the Austrian Empire. Taking away Sudetenland would strip a big chunk of Czechoslovakia's population and its only defensible border with Germany. But that's just what the British and French did without even letting the Czech representatives in the room.
There was no pretense of restoring an irredentia when Hitler attacked Poland, but the previous appeasements had let him build up his power.
After WWII, irredentism got a bad name because of its role in the causes of the War. It got another bad eye when India and Pakistan split off of British India and millions died because of Pakistan's insistence it had to have a Muslim country.
After WWII, the problem was solved be an exhange of populations rather than land. Millions of Poles were pushed west by the Russians. Millions of Germans fled from former German regions in Poland, Romania and Yugoslavia. Germans either left the German speaking regions of France and Belgium or settled down to become good citizens.
Well, all that has been forgotten and irredentism is back with a vengeance and very popular again in Europe. To the point where the Israeli "occupation" is "illegal." Never mind Israel conquered the territory in the 1973 War the Arabs started. Never mind that the sovereign powers, Jordan and Egypt ceded any claim to the land. Never mind that Arafat rejected a Pali state in 2000 in favor of a war he lost.
The solution was obvious after the 1948 war. The "camps" should have been disbanded and the inmates offered citizenship in the host Arab countries. But the UN rejected that for keeping the Palis in camps and fomented hatred by telling the world their irredentist claim not just on the West Bank and Gaza, but also on Israel itself, is justified.
ping.