This photograph from December 23, 1973, captures a common sight in the 1970s—cars lined up to buy gas, which was both expensive and in short supply. The gas shortage was linked to the oil crisis that began in 1973 when the United States decided to support its ally Israel in the Yom Kippur War against Egypt and Syria, which were in turn backed by the Soviet Union. The Cold War backdrop to the action in the Middle East solidified American resolve to support Israel, even after Arabian members of the Organization of Petroleum Exporting Companies (OPEC) enacted an oil embargo against the United States. Because the United States imported one-third of its oil from Arab nations, the embargo set off an oil crisis. The oil crisis, in turn, was the beginning of a prolonged downturn in the U.S. economy.