Bilateral relations between Saudi Arabia and the United States began in 1933 when full diplomatic relations were established. These relations were formalized under the 1951 Mutual Defense Assistance Agreement. Despite the differences between the two countries—an Islamic absolute monarchy versus a secular constitutional republic—the two countries have been allies ever since. The U.S. provides military protection to the Kingdom in exchange for a reliable oil supply, pricing of oil in U.S. dollars, and support for American foreign policy.
Ever since the modern relationship began in 1945, the U.S. has been willing to overlook some of the kingdom's domestic and foreign policy aspects as long as it maintained oil production and supported American national security policies.