Why did Russia built the Berlin Wall?

Related questions

1. Who actually tore down the Berlin Wall?
2. Is Alexanderplatz in East or West Berlin?
3. Why did Reagan tear down the wall?
4. Who took down the Berlin Wall?
5. Who ordered the Berlin Wall to be built?
6. How many people died crossing the Berlin Wall?
7. Who took the Berlin wall down?
8. What was the Berlin Wall known for?
9. Was the Berlin Wall effective?
10. Why was the Berlin Wall put up in the first place?

Tags

1. #guard
2. #built
3. #erected
4. #germany
5. #intruders
6. #berlin
7. #became
8. #borders
9. #reason
10. #separating
11. #doing
12. #fence
13. #identified
14. #union
15. #because
16. #democratic
17. #against
18. #communist
19. #soviet
20. #started
21. #wanted
22. #offical