The Kuwait–Najd War erupted in the aftermath of World War I. The war occurred because Ibn Saud wanted to annex Kuwait. The sharpened conflict between Kuwait and Najd led to the death of hundreds of Kuwaitis. The war resulted in sporadic border clashes throughout 1919-1920.
Following the Kuwait–Najd War, Ibn Saud imposed a trade blockade against Kuwait for 14 years from 1923 until 1937. The goal of the Saudi economic and military attacks on Kuwait was to annex as much of Kuwait's territory as possible. At the Uqair conference in 1922, the boundaries of Kuwait and Najd were set. Kuwait had no representative at the Uqair conference. Ibn Saud persuaded Sir Percy Cox to give him two-thirds of Kuwait's territory. More than half of Kuwait was lost due to Uqair. After the Uqair conference, Kuwait was still subjected to a Saudi economic blockade and intermittent Saudi raiding.
In 1913 the emir of Riyadh captured the Sanjak of Hasa from the Ottomans to become the new neighbor to the Emirate of Kuwait. According to the Anglo-Ottoman Convention of 1913, Kuwait's border extended south to Manifa (about 200 km from Kuwait city), but the Emirate of Najad didn't recognize the Convention since the Ottoman province annexed to Najd.
In 1919 Sheikh Salim Al-Mubarak Al-Sabah intended to build a commercial city in the south of Kuwait. This caused a diplomatic crisis with Najd, but Britain intervened, discouraging Sheikh Salim.
In 1920, an attempt by the Ikhwan to build a stronghold in southern Kuwait led to the Battle of Hamdh; Sheikh Salim then sent 300 men to intimidate the Ikhwan, but this led to a bloody battle and the defeat of Kuwaiti forces.
Kuwait's ruler asked help from emirate of Hail the enemies of emirate of Najd which sent troops to aid Kuwait, Sheikh Salim again sent all the troops to attack the Ikhwan, however they were ready to the battle so the Kuwaiti troops did not attack and returned to Jahra. Ikhwan forces (4,000 men) tracked them and raided Jahra; 40 km from the capital battles occurred in which the Kuwaitis were mostly victorious. Some 200 people were killed in the battle. In response, the British deployed gunboats, armored cars and aircraft. Eventually, the Bedouins withdrew.
^Reeva S. Simon, Philip Mattar, Richard W. Bulliet (1996). Encyclopedia of the Modern Middle East - Volume 1. p. 119. "Fighting between Kuwait's forces and Wahhabi supporters of Ibn Sa'ud broke out in May 1920, and the former were soundly defeated. Within a few weeks, the citizens of Kuwait constructed a new wall to protect Kuwait City."