On the 29th of August, Sir R. Hill, with the second division, entered Illerena, and pushed on to Ayllones, on the borders of Estremadura; but, finding the French were retrograding on Cordova and Granada, for the purpose of communicating with Joseph, who, in like manner, was forming a junction with the Duke of Albufera, intending to make Valencia the centre and the base of his future operations against Madrid; Sir R. Hill, thereupon, by a flank movement, marched towards the city of Medellin, on the left bank of the Guadiana, so as to be in readiness to act wherever his presence might be required, or to open his line with the third, fourth, and light divisions, cantoned in the vicinity of Madrid. The General-in-Chief no sooner saw a probability of his right flank being cleared of the enemy, than he set off from Madrid, and concentrated the first, fifth, sixth, and seventh divisions round Arevalo, (early in September,) with a force of cavalry and artillery, passed the Douro, and retook Valladolid, which had been re-occupied by the enemy for a short time. On the 19th he crossed the river Arlanzon, and laid siege to the old castle of Burgos, bristled with cannon and the bayonets of its hardy defenders. Various attempts by escalade, mining, explosions, and breaching were tried for a month without success, owing to the want of a sufficiency of battering artillery, and to the obstinate defence made by the enemy, who firmly lined the walls, and threw their balls and bullets with deadly aim against the assailants. The enemy's vanguard was at Briviesca, and his main body behind the river Ebro, during the greater part of the siege. In the mean time the second division had moved, in the middle of September, across the river Guadiana, through Truxillo Jaraceijo, towards Almaraz, and then crossed the Tagus by a pontoon bridge, and continuing its movement on the right of that river, passed Talavera de la Reyna, and arrived on the 30th at Toledo, occupying both banks of the river Tagus. General Sir Rowland Hill pushed forward his advance to Yepes and its vicinity, taking the command of the right wing of the army, composed of the second, third, fourth, and light divisions, besides cavalry and artillery stationed in the vicinity of Madrid. [Footnote 41: About forty-eight miles.] [Footnote 42: One of these mortars was brought to England, and is now placed on the south side of St. James's Park.] CHAPTER XI.