The basin of Vittoria is about twelve miles in length, from the defile of Salinas, where the river Zadorra enters it on the east, to the defile of Puebla, where the river quits it to flow towards the Ebro. The great royal road, the only one good enough for the enormous convoys with which the French army was burdened, traversed these defiles, running through the town of Vittoria on the south side of the river. The basin is more or less completely surrounded with hills, crossed by rough and difficult roads. To the west is the valley of the small river Bayas, which converges towards the Zadorra, joining the Ebro just above it. From the Bayas there is a way into the basin of Vittoria by a gap in the hills behind the village of Subijana de Morillos, four or five miles from the Puebla defile. A dozen miles higher up the Bayas the road from Bilbao crosses that stream, and threading the defiles of the northern hills comes down straight on Vittoria. The French, who were in fact to fight for the plunder of Spain and the accumulated material of the army, had been already weakened by large detachments sent forward in charge of convoys. Outnumbered in fact, outweighed still more in imagination, they were massed, except Reille's divisions, at the western end of the basin, the plain behind them being full of waggons of all descriptions. Reille was posted north of Vittoria, facing the Bilbao road, so far from the rest of the army that he could not possibly be supported if attacked by superior numbers, though it is obvious that if Reille were overpowered the great road would be lost. Nothing could better illustrate the extreme unwisdom of not standing to fight earlier: defeat at Vittoria meant the loss of everything, and the dispositions made invited defeat. Wellington fully realised his advantage: he sent Graham with some 20,000 men up the Bayas, to cross into the basin of Vittoria by the Bilbao road and attack Reille, while the rest of the army attacked the main body of the French posted behind the Zadorra at the west end of the basin.