 On 6 October, one week before the offensive was to commence, about 500 rebels crossed the border and attacked the town of Koboko.The 200-strong UNLA garrison was on parade at the time and was unarmed; the rebels massacred the soldiers.Word of the attack spread to other UNLA garrisons in West Nile, who quickly fled to the Nile River, leaving the Uganda Army's advance unopposed.