Notice: I'll edit my answer if I interpret this incorrectly.
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So rephrasing this and excluding certain parts, a new question can be made: <em>What were the reasons for division of Germany?</em>
At the Yalta conference after World War II, Germany was split into four zones of occupation; the occupying countries were the UK, France, the USA, and the USSR. Berlin was located in the USSR-occupied zone; as a result, the other allies insisted that Berlin be divided into four as well.
The elections that will take place the next year were intended to gradually bring Germany back together.
The US and USSR's wartime alliance—or, more generally, the tense partnership between communism and capitalism—started to break down once their shared opponent, Nazi Germany, was destroyed. Both the USSR and the western nations worried that Germany would elect a communist administration, while the USSR believed that Germany would maintain its capitalist system. Neither side trusted the other to conduct free and fair elections. Because neither side wanted to give up control over Germany, occupation continued.
The merging of three of the zones started between 1946 and 1949. First, the British and US zones amalgamated to become Bizonia, a semi-state, then the French joined them in Trizonia.
The USSR-run portion, meanwhile, remained strongly aligned with the USSR. The Cold War started to worsen and it became obvious that the alliance was gone during the Berlin Blockade of 1948–1949, when the Russians cut off what had become West Berlin from the outside world. West Berlin remained under the supervision of the UK, USA, and France, but West Germany as a whole was very different from East Germany.
Perhaps the most significant division occurred when "West Germany" joined NATO, an alliance primarily created to protect against communism, and "East Germany" joined the communist Warsaw Pact. They were now basically two distinct states, each with its own ideology.
Elections were conducted shortly afterward, and the two states formally separated from one another.
Germany was never designed to be divided into the east and west. The USSR and USA were completely distrusted, which led to the gradual and seemingly inevitable split.
Fortunately, the reunification of the two halves of Germany in 1990 was a historic event on both a national and global scale.
