After WWII, the victorious countries (France, the U.K., the U.S.A., and the Soviet Union) divided up control of Berlin, Germany's capital. They all signed a treaty saying that France, the U.K., and the U.S.A. each controlled a piece of Berlin on the west side of the city, while the Soviets controlled a piece on the east side. The deal was that all four countries were allowed to move freely in all four sectors of Berlin. They also divided up the whole country of Germany into four sections, and Berlin was completely surrounded by the Soviet Union's portion of the country. So when the Soviets decided to block off their section of the city, they were going against the rules of the treaty they had signed, and also made it very difficult for people in West Berlin to get food and supplies. So France, Britain, and the U.S.A. decided that it was important to protect their interests in West Berlin and to demonstrate to the Soviets that even building a wall around an entire city would not cause <span>France, Britain, and the U.S.A. to give up on West Berlin.</span>
They were against the berlin blockade so they helped the citizens on the other side so they didn't have to starve and so the people who put up the blockade saw that the allies would still help the citizens.
