Why was the Berlin Wall constructed

At the end of the World War II, the remainder of Nazi controlled Germany that lay on the western side of the Oder-Neisse line was divided into four occupational zones, and each of these zones was controlled by one of the four members of the Allied Power — America, Britain, France and Soviet Union. The city of Berlin became the capital of the Allied Control Council and it was also divided into four sectors.

In less than 2 years, the Allied Power split into two parts, with Soviet Union on one side, and Britain, France and America on the other. The main reason for discord was the reconstruction plan, which aimed a making Germany self-reliant. Soviet Union didn’t want to provide any kind of autonomy to post-war Germany, and for this reason, it opposed the reconstruction plan and decided to move apart.
Due to these differences, the city of Berlin was also divided into two parts, the eastern zone under the control of the Soviet Union was called the German Democratic Republic (GDR), and the western zone, which was controlled by America, Britain and France, was called the Federal Republic of Germany (FRG). Unlike East Germany, West Germany prospered under the reconstruction plan.

In a short span of time, FRG became capitalist economy with a democratic parliamentary government and social market economy. As the economy grew, the living standard of the people improved. The economy of GDR, on the other hand, crumpled under the oppressive communist rule. Due to the vast economic difference, the people of East Germany started moving towards the FRG.
To prevent the migration of people from east to west, the Eastern Bloc emigration restrictions were implemented. However, approximately 3.5 million people of GDR evaded the restrictions and escaped to West Germany. In a bid to prevent this uncontrollable brain drain, the Berlin Wall was constructed in 1961. For no less than a quarter century, the wall separated East Germany from West Germany, and also succeeded in plugging mass migration. Additionally, the Soviet Union was also able to re-assert its control over GDR.

On the whole, the Berlin Wall was public-relation disaster; families were separated, people lost their jobs, and there was widespread discord and unrest. With the passage of time, enormous pressure mounted on the GDR Government, and on 9th November 1989, the government allowed all the citizens of East Germany to visit FGR. With the fall of the Berlin Wall, the two zones of Germany united and the communist rule came to an end not only in GDR, but also throughout Europe.