The Kingdom of Saudi Arabia is located in the southwest of the continent of Asia, it represents  the largest part of the Arabian Peninsula, with a land area of ​​approximately two million square kilometers. It is bordered on the north by Iraq and Jordan while bordered by Kuwait from the northeast, and on the east it is bordered by Qatar and the United Arab Emirates, in addition to Bahrain. the Later is linked with Saudi km through  King Fahd Causeway on the Arabian Gulf, and Yemen from the south. While, Oman from the southeast, as well as  the Red Sea From the west.

the shape of Saudi Arabia has not been appeared as it is known today, except it is going through three historical periods which began in the eighteenth century AD.

 
The 1st period of Saudi Arabia state (1744AD-1818AD):

The first period of Saudi Arabia has been initiated  with the stability of (Muhammad bin Saud bin Muqrin) in Al-Dir'iyah and the second after its prince Zaid bin Markhan bin Watban. Muhammad bin Saud bin Muqran) was appointed as its prince in (1727 AD). He declared AlDir’yah as the capital of his properties which expand and became independent in his rule in (1744 AD) and called himself (al- Imam). Thus, he became the 1st  imam of 1st  Saudi period. He- the only political ruler-and Mohammad bin abdulwhab- the religious scholar(to him the Wahhabi doctrine is attributed- have been together  and subject all the lands of the Arabian Peninsula under the rule of one man with the name of the reformist call; so they agreed on a contract which is known with the Charter of Diriyah(ALDiriyah agreement) (1745 AD).

(Muhammad bin Saud) was busy with the developments of neighborhoods and all regions under his rule, so he established castles, forts, palaces in addition to the towers. Then he built the wall of Diriyah in (1758). He has been the ruler of Alduriah in the 1st period of kingdom of Saudi Arabia until the year(1765). Then his son became after Mohammad bin turki. Abdulaziz bin Mohammad, the son of Mohammmad bin Saud who followed back his father’s steps. He put all of the smalltowns and villages under his control, while his fights and wars expanded until Aleraq, where the other successors and Othmanin felt of his strength and ability, they fight him in AlDiriyah But he confronted them and repelled them from it, and his rule lasted from 1765 AD until his assassination in 1803 AD. His son who is known as Saud al-Kabir, followed him and continued the path of his predecessors, and ruled for about 11 years from 1803 - 1813 and passed away in 1814 .

Then his son Abdullah bin Saud came after his father, who did not spend more than five years, because of  Ottoman Sultanate victory which has been terminated with retrieve of al-Diriyah and all its lands under the leadership of the army (Ibrahim Pasha). Pasha blockade Diriyah for a whole year until he forced (Abdullah bin Saud To surrender himself to Ibrahim Pasha, who sent (Abdullah bin Saud) to Cairo, and then to Astana, he was executed there in 1818 . Thus, Dir'iyah or the first Saudi kingdom became again under Ottoman rule.

The 2nd period of Saudi State (1824-1891)

When Othmanian empire settlement took place in ALDIRIYAH, it had been completely destroyed, even its wall, and immediately the empire was preoccupied with its wars with the countries of Europe .meanwhile, its powers and forces vanished in Saudi lands, which led to the non-existence of its power in ALDIRIYAH. As a consequence the conflicts among tribes have been raised once more. Thus, Muhammad bin Mishari Al Muammar endeavored to rebuild ALDIRIYAH again, but he failed. Hit-and-run were raised at that time, as so the internal fights and conflicts between Muhammad bin Mishari Al Muammar and Mishari bin Saud -who had been selected by  most of the Saud family- whom ran away from Dir'iyah- because the blockage of Ibrahim Pasha. where the forced of Ibraheem had lead Muhammad bin Mishari Al Muammar to pledged allegiance to Mishari bin Saud by  coercion, and soon he was betrayed and seized power, and declared that his loyalty to the othmanina Sultan and the Ottoman Empire only, in order to avoid a fight with them, so they saved his emirate.

Meanwhile, and during the blockade of 1st period of Saudi Arabia state,Turki bin mohammad al saud cooprated with ABDULLAH bin saud- they put their hands together- when ebraheem pasha could controlled ALDIRIYAH, Turki bin Abdullah ran a way  TO alriydh and declared himself as its prince and alryiadh is the Capital of the second Saudi Arabia state. But, the fight had not terminated between bin moaamar and mosharibin saud.Turki bin Abdullah had attacked ALDIRYAH and especially after the clarity of almoammar’sdeception. Alturki handed almoammar and his son over to othmanina forces and they have been punished withexecution since mammar’s and  his son’s killing of moshari bin saud .othmanina empire forces recognized bin Turki insecurity;  the empire sieged him, but he ran a way and built the strongest heart as a resistance against the Othmanian empire.  

In 1828, AlRIYDH became under Turki bin Abdullah’s controls. So, All regions of Najd were condemned for his allegiance, Al-Ahsa ,Oman and Bahrain pledged allegiance to him, too. The security and judgments had been raised during his ruling. He took Muhammad Ali’s forces out of Najd, supported mobammad bin abdulwhaband served the courts, but his cousin-moshari binabdulrhman AL SAUD- had made a conspiracy to assassinate him. SO, he died. Although, the cousin of him had not spend more than forty days in his ruling. Immediately, Faisal bin Turki Al Saud regained the power and then assigned Khalid bin Saud Al Saud In the emirate by the forces of Muhammad Ali Pasha Thus, the events of struggles in the second Saudi period continued between the sons of Faisal for power and the revolt of princes against each other.so about eight princes took over this state until its end after (the Battle of Haremla). In this way, the rule once again out of Saudi hand -of the House of Saud- returned to the Ottoman empire.

The Third period of SAUDI ARABIA( Modern Saudi state) (1902-now):

In the year (1902AD), prince Abdulaziz bin Abdul Rahman bin Faisal Al Saud had returned back alRiyadh to recover it and proclaimed himself as prince over it. Then, Abdulaziz Al Saud was able to bringing all areas of Najd together  and the kingdom was known as the Sultanate of Najd, besides that he would include the Kingdom of Hejaz to become the king of - The Kingdom of Alhejaz ,Nejd and all its related areas-until the year 1932- which was the year of Kingdom of Saudi Arabia establishment with all its borders and lands known today.thus, abdulaziz bin abdulrhman bin faisel al saud is the king for the modern Saudi Arabia and who continued in his position more than fort four years, he died in his palace. king Abdluaziz had the main hand of forming the modren Saudi Arabia, he had been followed by six kings:

1-SAUD BIN ABDULAZIZ AL SAUD.

2-FAISEL BIN ABDILAZIZ AL SAUD.

3-KHALED BIN ABDULAZIZ AL SAUD.

4-FAHAD BIN ABDULAZIZ AL SAUD.

5-ABDUALLAH BIN ABDUALZIZ AL SAUD.

6-SALAMAN BIN ABDUALZIZ AL SAUD.

Resource: 

‏https://almoheet.net/قصة-توحيد-المملكة-العربية-السعودية/