A second, smaller Saudi state (Emirate of Nejd) lasted from 1819–1891.Its borders being within Najd, Wahhabism was protected from further Ottoman or Egyptian campaigns by the Najd's isolation, lack of valuable resources, and that era's limited communication and transportation.Estimates of the number of adherents to Wahhabism vary, with one source (Mehrdad Izady) giving a figure of fewer than 5 million Wahhabis in the Persian Gulf region (compared to 28.5 million Sunnis and 89 million Shia).
It was at this time, according to De Long-Bas, that Wahhabis embraced the ideas of Ibn Taymiyya, which allow self-professed Muslims who do not follow Islamic law to be declared non-Muslims – to justify their warring and conquering the Muslim Sharifs of Hijaz.
One of their most noteworthy and controversial attacks was on Karbala in 1802.
According to most sources, Ibn Abd al-Wahhab declared jihad against neighboring tribes, whose practices of asking saints for their intercession, making pilgrimages to tombs and special mosques, he believed to be the work of idolaters/unbelievers.
It was only after the death of Muhammad bin Saud in 1765 that, according to De Long-Bas, Muhammad bin Saud's son and successor, Abdul-Aziz bin Muhammad, used a "convert or die" approach to expand his domain, However, various scholars, including Simon Ross Valentine, have strongly rejected such a view of Wahhab, arguing that "the image of Abd’al-Wahhab presented by De Long-Bas is to be seen for what it is, namely a re-writing of history that flies in the face of historical fact".
With the collapse of the Ottoman Empire after World War I, the Al Saud dynasty, and with it Wahhabism, spread to the holy cities of Mecca and Medina.
After the discovery of petroleum near the Persian Gulf in 1939, it had access to oil export revenues, revenue that grew to billions of dollars.
The British also adopted it and expanded its use in the Middle East.
Wahhabis do not like – or at least did not like – the term.
The result that safeguarded the vision of Islam-based on the tenets of Islam as preached by Muhammad ibn Abd al-Wahhab was not bloodless, as 40,000 public executions and 350,000 amputations were carried out during its course, according to some estimates.
Under the reign of Abdul-Aziz, "political considerations trumped religious idealism" favored by pious Wahhabis.
advocating a purging of such widespread Sunni practices as the veneration of saints and the visiting of their tombs and shrines, all of which were practiced all over the Islamic world, but which he considered idolatry (shirk), impurities and innovations in Islam (Bid'ah).