National Day is celebrated each year on September 23, the anniversary of the day in 1932 when King Abdulaziz bin Abdulrahman Al-Saud declared the establishment of the Kingdom of Saudi Arabia after thirty years of struggle following his re-taking of the Masmak Fortress in Riyadh in 1902. The Saudi state itself dates back to the 18th century, when Muhammad bin Saud, inspired by the call of Sheikh Muhammad bin Abdulwahab, pledged service to God and protection of the faith of Islam in ruling his people.