On 5 November 2009, the Royal Saudi Land Forces launched a sweeping ground offensive against Yemen's Shiite Houthi rebels after they crossed the Saudi border in order to outflank the Yemeni Army, which had launched a military campaign against the Houthis to control and pacify the northern Yemeni mountains, and killed two Saudi border guards. The Saudi forces relied heavily on air power and artillery to soften the rebels without risking their men. The Saudi Army lost 133 soldiers in the fighting against the rebels, with most of the casualties occurring when ground forces tried to move into areas that had been softened by shelling that "raised alarms across the Sunni Arab world about the possibility that Iran might be supporting the Yemeni rebels".