Saudi Arabia is the birthplace of Islam and home to Islam's two holiest shrines in Mecca and Medina. The king's official title is the Custodian of the Two Holy Mosques. The modern Saudi state was founded in 1932 by ABD AL-AZIZ bin Abd al-Rahman AL SAUD (Ibn Saud) after a 30-year campaign to unify most of the Arabian Peninsula. A male descendent of Ibn Saud, his son ABDALLAH bin Abd al-Aziz, rules the country today as required by the country's 1992 Basic Law. Following Iraq's invasion of Kuwait in 1990, Saudi Arabia accepted the Kuwaiti royal family and 400,000 refugees while allowing Western and Arab troops to deploy on its soil for the liberation of Kuwait the following year. The continuing presence of foreign troops on Saudi soil after the liberation of Kuwait became a source of tension between the royal family and the public until all operational US troops left the country in 2003. Major terrorist attacks in May and November 2003 spurred a strong on-going campaign against domestic terrorism and extremism. King ABDALLAH has continued the cautious reform program begun when he was crown prince. To promote increased political participation, the government held elections nationwide from February through April 2005 for half the members of 179 municipal councils. In December 2005, King ABDALLAH completed the process by appointing the remaining members of the advisory municipal councils. The king instituted an Inter-Faith Dialogue initiative in 2008 to encourage religious tolerance on a global level; in February 2009, he reshuffled the cabinet, which led to more moderates holding ministerial and judicial positions, and appointed the first female to the cabinet. The country remains a leading producer of oil and natural gas and holds more than 20% of the world's proven oil reserves. The government continues to pursue economic reform and diversification, particularly since Saudi Arabia's accession to the WTO in December 2005, and promotes foreign investment in the kingdom. A burgeoning population, aquifer depletion, and an economy largely dependent on petroleum output and prices are all ongoing governmental concerns.