In the winter of 1931/1932, in response to a Yemeni unit invading Najran and destroying Saudi property, Khalid bin Luwai arrived in Najran with his forces and clashed with Yemeni troops.

All known details are provided on page 322 of St John Philby's 1955 book Saudi Arabia, which gives the following account:[2]But in the winter of 1931/2 a more serious incident occurred, when a Yamani force descended on and occupied Najran, where the property of unfriendly elements was destroyed.

The Najran issue was thus settled for good.The conflict is also mentioned on page 54 of Nadav Safran's 1988 book Saudi Arabia: The Ceaseless Quest for Security,[3] which gives a similar account, likely based on that of Philby:[4] The immediate cause of the Yemen war was a dispute over the oasis of Najran, on the border between the two countries, which the forces of Imam Yahya seized and from which the Ikhwan ousted them in the spring of 1932.

In an enquiry in 2017, the Correlates of War project was unable to find any further information, and found that The Times did not contain any mention of such incident.

We're not given great information about how to separate an attack from a clash or a show of force from an occupation of territory at the incident-level.