History of Saudi Arabia

The beginning of the modern history of the state of Saudi Arabia is argueably when an Islamic reformer named Muhammad ibn Abd al Wahhab and a local ruler named Muhammad bin Saud founded the Emirate of Diriyah in the year 1744. It was founded in the area of Nejd, the central part of the Arabian Peninsula. The Sa'udi emirate's leadership can be viewed as a traditional form of rule within communities of Arabia in the 18th century. Over the next century and a half the family went through a lot of opposition and hurdles. The family faced opposition from powerful families of Arabia but also rulers of Egypt and the Ottoman Empire.
In 1902 Abdul Aziz Ibn Saud, also known as Abdul Aziz Al-Saud, took over the city of Riyadh from another family named Al-Rashid. He continued to win more areas, and on 8 January 1926, he became the King of Hejaz and the Sultan of Nejd. On 20 May in 1927, the government of the United Kingdom accepted him as the King of those areas ruled by him (the Nejd and Hejaz). His kingdom now became a sovereignty. The modern nation state of Saudi Arabia was established in 1932 as 'the Kingdom of Saudi Arabia' declared by King Abdul-Aziz Al-Saud. Petroleum oil was found in Saudi Arabia on 3 March in 1938, which made the country rich since the export of oil started to bring in a lot of money.
But the history of the Arabian Peninsula contains more history, which led to the development of the Saudi state. Inhabitants and cultures can be traced back 63,000 years ago. The most significant event that happened in the Peninsula is the rise of the Islamic religion presented by Prophet Muhammad. The Rashidun Caliphate, Umayyad Caliphate, Abbasid Caliphate and Fatimid Caliphate all occupied the Arabian Peninsula and thus helped it develop to how we know it today. More dynasties were there in history, but the Islamic holy cities of Mecca and Medina were under the protection of the Hashemite Sharifs of Mecca from the 10th century onwards.
Early history.
Pre-Islamic Arabia.
When discussing pre-Islamic Arabia, we refer to the time before 610 CE. This is the year when the Prophet Muhammad started propagating the religion of Islam and thus when the religion of Islam started to form. The term ‘pre-Islamic Arabia’ is useful because it signals the importance of Islam and its influence in forming the Peninsula as we know it today with all its religions and cultures. But it also shows a relation between the rise of Islam and the native Arabs conquering the world through conquest, trade and innovations.
This era covers thousands of years with a lot of different cultures and communities. The oldest evidences that point to inhabitants of the Peninsula are estimated to be 63,000 years old. There are inhabitants that had trading relations with many parts of the ancient world, but the hot and harsh climate had made large settlements difficult. So bedouin groups were naturally also present. Some settlements had always existed around oases; these are places in the deserts where growth and water are available. For instance there was a culture called the Dilmun culture among them, which was very old and existed along the Persian Gulf. It was as old as the ancient civilizations of the Sumerians and Egyptians. But also the Kindite kingdom and other ancient communities were present.
It is better to refer to the History of Arabia Wiki page when discussing the Pre-Islamic era. This page (History of Saudi Arabia) will cover more of the Post-Islamic era because of its strong relationship with Saudi Arabia. 
Post-Islamic Arabia.
The birth of Islam.
The Hejaz area became an important center as Islam rose in the 620s. After Prophet Muhammad of the Quraysh tribe started calling to Islam in 610, the already existing cities of Medina (formerly called "Yathrib") and Mecca eventually became the holiest places of Islam and thus most of Muslims. The number of followers rapidly began to grow after the migration (or Hijra) of Muhammad and his companions in 622 from Mecca to Medina. During the completion of the religion, both these cities became the holiest places in the Muslim World. Masjid al-Haram and Al-Masjid al-Nabaw I am the main locations of pilgrimage where Muslim hopes to visit the Kaaba primarily in Masjid al-Haram and the Prophet's tomb in Al-Masjid al-Nabawi at least once in their lifetime.
Muhammad and his companions went through the Arabian Peninsula in the following years and united the divided tribes of Arabia under one flag. This led to Medina becoming the capital of the newly established Islamic state ruled by the Prophet Muhammad.
After Muhammad died in 632, a new head of the state, called caliph, was named: Abu Bakr. He was the first of the four caliphs whose caliphate was called that of the Rashidun, which means 'rightly guided.' After dealing with the Ridda wars, wars against rebellious tribes who rebelled after Muhammad's death, he started to campaign against the Byzantines. Abu Bakr himself did not live to see the results of his initiative after suffering a natural death in 634. But his successors sure did.
Umar was the second caliph and managed to lead the Muslims to conquer Roman Egypt and even expand to present day Libya in the west. All the way to eventually the Indus River in the east after conquering the Sassanid Empire. Eventually in 644 it was neither the past famines or plagues that killed Umar, but a Persian slave.
Uthman ibn Affan followed Umar as a caliph and ruled the longest of the four caliphs. In his twelve years of rule he standardized the Qur'an, spread the empire westwards to the Maghreb and even a part of Spain and eastward further into Central Asia. He was also assasinated which lead to Ali ibn Abi Talib being the fourth Sunni caliph and the first Shia imam.
The Umayyad and Abbasid Empire.
The death and assassination of Ali ibn Abi Talib in 661 gave birth to a new era where the Umayyad Caliphate thrived and continued to expand the land left by the Rashidun.
Modern history.
Wahhabism and the First Saudi State.
After Muhammad ibn Abd al Wahhab got exiled from Uyaynah, he sought refuge in Diriyah, where some of his followers were residing. At that time, Muhammad bin Saud was the local chieftain of Diriyah. Two brothers and the wife of Muhammad bin Saud were followers of Muhammad ibn Abd al Wahhab's ideology. They encouraged cooperation between Muhammad bin Saud and Muhammad ibn Abd al Wahhab. Muhammad ibn Abd al Wahhab needed military support to secure his ideology and preaching, while Muhammad bin Saud needed pastoral support. Fulfilling these needs eventually led to an alliance between the scholar Muhammad ibn Abd al Wahhab and the local ruler Muhammad bin Saud creating the First Saudi State, the Emirate of Diriyah.
When Muhammad bin Saud died in 1765, his son Abdulaziz bin Muhammad Al Saud who was a dedicated student of Muhammad ibn Abd al Wahhab, became the leader of the Emirate of Diriyah. In his reign, the Emirate of Diriyah expanded in territory throughout the Arabian Peninsula. In the eastern part of the peninsula, Abdulaziz bin Muhammad Al Saud got Al-Hasa, Qatar, Al-Buraimi and Bahrain under his influence. In the western part of the Peninsula, Abdulaziz bin Muhammad Al Saud conquered parts of the Hejaz region. During the conquests of Abdulaziz bin Muhammad Al Saud, the Saudi State got involved in a war with the Ottomans. At this stage, the campaigns of the Ottomans against the Saudi State failed, and Abdulaziz bin Muhammad Al Saud was expanding his territory inside Ottoman territories. With the death of Abdulaziz bin Muhammad Al Saud in 1803, his son Saud bin Abdulaziz Al Saud became ruler. Saud bin Abdulaziz Al Saud conquered the holy cities of Mecca and Medina for a few years, which gave him the title of Custodian of the Two Holy Mosques. Eventually the Egyptians, who were supported and led by the Ottomans, destroyed the powers of Al Saud in 1818. It marked the end of the First Saudi State. 
Ottoman domination.
By 1824, the Al Saud family regained control over parts of the Nejd region. This is seen as the beginning of the Second Saudi State, the Emirate of Nejd. The Saudi ruler, Turki bin Ali, made Riyadh the capital of its state. It remains the capital of the Saudi State today. Turki bin Ali succeeded in retaking most of the lands lost to the Ottomans. In 1865 the Ottomans launched an attack on the Saudi State again. This time with help from the Al Rasheed family of Ha'il, who are another powerful family of the Nejd region. The Al Rasheed family defeated the Saudi State in 1891, which marked the end of the Second Saudi State. Abdul Rahman bin Faisal Al Saud, who was the Saudi leader at that time, retreated into the desert and eventually to Kuwait with his family.
Kingdom of Saudi Arabia.
In 1902, Abdul Rahman's son Abdulaziz regained Saudi territory from the Al Rasheed family. He even regained control over Mecca and Medina from 1924 to 1925. In 1932 he declared the Kingdom of Saudi Arabia, as it is known till today.
Boundaries.
The discussion for Saudi Arabia to fixate definite boundaries with its neighboring countries started from 1920 onwards. It finalized its boundaries with Iraq, Jordan, and Kuwait. On borders with Iraq and Kuwait, two neutral zones were created – one with Iraq and the other one with Kuwait. In 1934, borders with Yemen were almost finalized.In 1965, Saudi Arabia gave some of its areas to Jordan, and Jordan gave some of its areas to Saudi Arabia. In 1971, the neutral zone between Saudi Arabia and Kuwait was split between these two countries. Likewise, Saudi Arabia and Iraq decided in 1981 to split the neutral zone between them. This zone was split between the two countries in 1984.
Still, Saudi Arabia's borders with the United Arab Emirates and Oman were not final. The border with Qatar was finalized in 2001.
Politics.
King Abdul Aziz Al-Saud died in 1953. His son, who was named Saud, became the king. He reigned for 11 years. In 1964, he was forced to step down, and his half-brother, Faisal, became the king. Faisal had the support of the senior members of the royal family and the religious leaders. Faisal also held the post of the Prime Minister. This tradition of being both the King and the Prime Minister still continues in Saudi Arabia. All Kings after Faisal have followed this practice.
Faisal took several new steps for economic development of Saudi Arabia. During his reign, many important political events also happened like the ones noted below:
In 1975, King Faisal was assassinated by one of his nephews. The nephew was found guilty, and he was sentenced to death. King Faisal's half-brother Khalid became the King and the Prime Minister of Saudi Arabia. During the reign of King Khalid, Saudi Arabia's importance in regional politics increased. The economic growth of the country also continued at a steady rate until his death.
King Fahd's period.
King Khalid died in 1982. After his death, Fahd became the King. At the same time, he also became the Prime Minister of Saudi Arabia. His half-brother Prince Abdullah became the Crown Prince.
The income of Saudi Arabia became less during King Fahd's reign. This was a result of lower price of petroleum oil. King Fahd's government used an economic policy that helped the country to survive with a lower income.
King Fahd helped Iraq during the Iran-Iraq war. Iraq's economy had become terrible on account of this war. The King also discussed with these two countries to stop fighting. Both countries (Iran and Iraq) stopped the fight in August 1988. The King also helped in making the Gulf Cooperation Council (GCC) a more vital organization. The GCC is an organization of six countries Persian Gulf. The purpose of the organization is to increase the development of and cooperation among the member countries.
Gulf War.
In 1990, Saddam Hussain was ruling Iraq. The Gulf War of 1991 was when he invaded Kuwait. Many people thought that his army would also invade Saudi Arabia. King Fahd allowed some Western countries and the USA to send their forces to the country. Many Muslims were against that their most holy land was used by non-Muslim soldiers.
During and after the Gulf War, King Fahd’s role was vital. During the war, he allowed the entry of the royal family of Kuwait inside Saudi Arabia and was followed by 400,000 other persons from Kuwait to stay temporarily. The King let the troops of countries like the USA mount attacks on Kuwait to liberate it. He also helped arrange support from former Muslim countries for the liberation of Kuwait. Iraqi forces were eventually ousted from Kuwait.
Terrorism.
The presence of troops from Western countries has angered many Muslims. One of them was the rich man Osama bin Laden. He was forced to leave Saudi Arabia when he disagreed and opposed the King of Saudi Arabia. Other than Osma bin Laden and his followers, several other persons and groups did not like the presence of Western troops inside Saudi Arabia.
Those who opposed the presence of Western troops were persons and groups who attacked people. They tried mainly to attack the foreign forces in Saudi Arabia. Some examples of such attacks are given below:
The September 11, 2001 attacks in New York had resulted into many deaths and big destruction. After enquiry, it came to light that out of 19 suspected persons for these attacks, 15 were from Saudi Arabia.
Such things attracted the attention of the government of Saudi Arabia. The government started a policy to check such activities. Even then, terrorist activities of such persons and groups continued.