Specifically named was the 20 Brigade from Hafr al-Batin (on the border with Iraq) as well as three from Khamis Mushayt in the south: the 4th Armored Brigade, it's supporting 11th Brigade and the 18th Brigade. The 7th, 8th, 12th and Parachute Brigades were already deployed in Tabuk.
The sources refused to reveal the reason behind the deployment of these forces, which had been shrouded with secrecy. Other sources hinted that these movements came as a reaction to Israeli deployments near Saudi Arabia's southern border; which is separated from Israel by a strip of Jordanian territory less than 25 kilometers wide. Supposedly, Israeli violations of Saudi airspace had recently escalated "in a provocative manner". Standing instructions to the Saudi Air Force and Air Defense were to intercept, but not engage, Israeli planes.
Shortly thereafter, the Kingdom of Saudi Arabia TV1 evening broadcast announced that the Saudi Armed Forces were conducting routine exercises in the northwestern region and denied that it was a deliberate build-up. - Adam Geibel
The pro-government Saudi Arabian newspaper "Al-Khalij" on 23 April quoted informed sources' claims that orders had been issued to Saudi Armed Forces commanders during the week prior to reinforce the forces stationed in Tabuk area, near the Jordanian border.