In such a constricted corridor as the Zize Pass, which in average was less than 4 meters wide (13 feet), an army consisting of two legions, or roughly 20,000 men, along with about 800 wagons pulled by 1,600 draft animals, would stretch approximately 11 to 14 kilometers. Consequently, while the vanguard approached Gainekoleta (merely 3.4 km or 2 miles from the town of Luzaide), the rear would still be near Errozabal, hours apart in marching time. Moreover, the two segments of the army would be divided by the mountain pass at Ibañeta, out of sight from each other and forced to rely on sound signals for communication. The distance of about 14 kilometers (around 9 miles) from the edge of the Errozabal plain to the vicinity of Luzaide aligns with the distances described by historical sources.
The Basques, hidden among the beech trees on the mountain slopes that overlook the road, specifically on the left side, bided their time as the army passed through the Ibañeta Pass.
They launched their attack soon after on the central section of the army; as the rear guard was making its ascent through the Otezilo Ravine in their way to Ibañeta, the central troops were navigating down the Zize Pass after passing Ibañeta, and the vanguard was nearing Gainekoleta.
As the Saxon Poet describes, the initial assault originated from the hilltops to the left of the path, where they "first hurled their missiles from the heights."
