[kearnyirish2]

When Franco won the civil war in Spain in 1939, he declared all property titles issued after July 18, 1936 (the start of the war - and wealth re-distirbution by the Reds) null and void. Easy enough (since much less time had elapsed).

[Cronos]

In Poland's case, it's not that simple -- remember that not only did 20% of the population die during the war, but many escaped communism later and then Poland itself was moved 200 miles to the west -- Polish territory in what is now Western Belarus and Western Ukraine was taken by the USSR and Poland got the land east of the Oder-Niesse river

the property titles are utterly mixed and quite a lot destroyed as well.