Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

After the expulsion of the German population ethnic Russians, Belarusians, and Ukrainians were settled in the northern part. In the Soviet part of the region, a policy of eliminating all remnants of German history was pursued. All German place names were replaced by new Russian names. The exclave was a military zone, which was closed to foreigners; Soviet citizens could only enter with special permission. In 1967 the remnants of Königsberg Castle were demolished on the orders of Leonid Brezhnev to make way for a new "House of the Soviets".
Once the German populations was removed, what three groups  settled into the nothern area?