The Kingdom of Saudi Arabia is located in the southwestern part of the continent of Asia; it occupies four-fifths of the Arabian Peninsula. It is bordered by the Red Sea from the west, the Arab Gulf, United Arab Emirates, and Qatar from the east, Kuwait, Iraq, and Jordan from the north, and by Yemen and the Sultanate of Oman from the south.
The first Saudi State was established by Imam Muhammad bin Saud, who took over Al-Dir'iya state in 1139 AH / 1727 after the death of its Prince Zaid bin Markhan bin Watban, and later; it became a starting center of the establishment of the first Saudi state.
In Jumada II 1233 AH / April 1818, Ibrahim Pasha besieged Al-Dir'iya, and defeated the Saudi forces after many battles, and the Imam Abdullah bin Saud had surrendered in the 8th of Dhu al-Qi'dah 1233 AH / 1818. This ended the first Saudi state, which has extended its influence to most parts of the Arabian Peninsula.
In year 1238 AH / 1822, Prince Turki bin Abdullah re-established the Saudi state, and announced Riyadh to be its capital, where he began his ruling in year 1240 AH / 1824 after the surrendering of the Egyptian Ottoman garrison in Riyadh to him.
In Safar 1309 AH / September 1891, Abdullah bin Rasheed was able to defeat the army of Imam AbdulRahman bin Faisal and kill a number of his men, and he -Ibn Rasheed- continued creeping to Riyadh and ordered to demolish the walls of the city, and the two castles of its rulers, the old one and the new one; this ended the era of the Second Saudi State.
In the 5th of Shawwal 1319 AH / January the 15th, 1902, King AbdulAziz bin AbdulRahman bin Faisal Al Saud managed to retrieve back Riyadh and return to it with his family.
And on the 17th of Jumada I 1351 AH / September the 19th 1932, he announced the unification of the country and named it (The Kingdom of Saudi Arabia), starting from Thursday, the 21st of Jumada I 1351 AH / September the 23rd 1932 (the first day of Libra). And with this announcement, the Kingdom of Saudi Arabia was established and has become a great nation in its mission, achievements, and its regional and international status. After that, the first of Libra, corresponding to September the 23rd, was announced to become the National Day of the Kingdom of Saudi Arabia.