After the war, the west and the Soviets divided up the cadaver of defeated Germany, each side laying claim to as much as it could. The two motivations were different, however.
Russia, which had been devastated (some 20–25 million dead) and treated with complete savagery by the Nazis, wanted reparations and revenge. With their own factories west of the Urals destroyed, they transported as much of Germany’s industry as possible into Russia. The Soviets were also keen on keeping (and ideally expanding) communism in Germany, and created/allowed German communists to take power in their (East) zone.
While the UK had suffered great damage in the war, its industry was still operative, and the US had even prospered from its war industries, and had less than a million casualties. Consequently, the US had significantly less rage toward Germany. Politically, there were already great tensions even during the war between the anti-communist west and Russia, so the west was primarily interested in rebuilding Germany as a democracy as a buffer between the west and the Soviet Union. Americans, in particular, had much reason to hate Germans than the Russians.
Anyhow, with that tension already longstanding, it galled the Soviets to have the west claim half of the capital Berlin, which was way inside of the Soviet zone, and they kept up an ongoing claim that the west was trying to dominate Germany. When the three western powers combined their zones to form West Germany, and then West Berlin, and then, the greatest insult of all, to introduce a new currency (the Deutschmark) over their objections, the Soviets snapped.
The western forces had withdrawn most of their troops by 1948, while the Soviets still had millions of man, and so, ironically, they could have militarily driven the west out of Berlin. But Stalin seemed unwilling to risk a renewal of battle, this time with the US/UK, and so embarked on a program of harassment. The only WRITTEN terms of agreement between the west and the Soviets had been an agreement to have three air corridors from the west to Berlin, so — although they could have closed those, too, the Soviets did not — again, to avoid open battle with the west.
Back to the US. Pres. Truman, through George Marshall (and Congress, of course), devise the Marshall Plan, the financing (from the only country that still had financial assets) of all forms of reconstruction in Europe.
When the Soviets closed all traffic from the west to Berlin - except those three air corridors — the west already had a policy to supply, and it was therefore only a strategic matter of figuring out how to get aid and supplies to Berlin. At first, it was an awkward “cowboy” operation, primarily for lack of planes and pilots (and landing space on two moderately sized airfields), but the US - and to a lesser extent the UK - was able to call in air teams from Hawaii and Alaska, and after a few months, (and later, with the construction of a third French airfield at Tegel) they got organized and managed to supply a city of two million people with food and coal. At its peak, the circuit was bringing in planes every four minutes.
Even through the terrible winter of 48/49, the planes were able to bring in enough coal to keep the bakeries, trams, sewage and water supply systems in operation, though only enough to provide tiny amounts of power to private homes. People still died of cold and hunger, but a tiny fraction of what would have happened without the airlift.
After about a year, the Soviets realized that the west was not going to leave Berlin, and in June of 1949, they re-opened the roads, railways, and waterways.
It was the west’s finest hour — and the beginning of the Cold War.
