Wellington’s first task was to drawback his rearguard to join his main body, without allowing it to become seriously engaged with the great mass of French in its front. This he undertook in person, marching at daylight with all his disposable cavalry, the brigades of Bock and Le Marchant, to join the force at Castrejon, while he threw out the 5th Division to Torrecilla de la Orden to act as a supporting échelon on the flank of the retiring detachment. The remaining divisions (1st, 3rd, 6th, 7th) took up a position in line of battle on the heights above the Guarena, ready to receive their comrades when they should appear.
The charge of the rearguard this day was in the hands of Stapleton Cotton, the senior cavalry officer with the army, who outranked Cole and Charles Alten, the commanders of the 4th and Light Divisions. He had received no orders during the night, and his last, those of the preceding afternoon, had directed him to halt, till his chief should have discovered the true position and aim of the French army. Wellington explained, in his next dispatch home, that the various details of intelligence, which enabled him to grasp Marmont’s whole plan, did not reach him till so late on the 17th that it was useless to send Cotton orders to start. They could only be carried out at dawn, and he himself intended to be present with the rearguard before the sun was far above the horizon. He arrived at seven o’clock in the morning, in time to find his lieutenant already engaged with the French van, but not committed to any dangerous close fighting. Cotton had, very wisely, sent out patrols before daylight to discover exactly what was in front of him; if it was only a trifling body he intended to drive it in, and advance towards La Nava and Rueda[479]; if Marmont was in force he would take up a defensive position at Castrejon, and wait for further orders.
The patrols soon ran into French cavalry advancing in force, and were driven back upon Anson’s brigade, which was drawn up on a long front in advance of the village of Castrejon. On seeing it, the enemy brought up two batteries of horse artillery, and began to play upon the scattered squadrons. Bull’s and Ross’s troops[480] were ordered out to reply, and did so with effect, but the total strength of the French cavalry was too great, and Anson’s regiments had presently to give way, though not so much owing to the pressure on their front as to the sight of a large column of French infantry turning the left of their line, and marching on Alaejos, with the obvious intention of getting round to their left rear and molesting their retreat towards the Guarena, where the main body of the British army was awaiting them.
Wellington was involved in person in the end of the cavalry bickering, and in no very pleasant fashion. He and Beresford, with their staffs, had arrived on the field about seven o’clock, in advance of the two heavy cavalry brigades, who were coming up to reinforce Cotton. He rode forward to the left of the skirmishing line, where two squadrons, one of the 11th and one of the 12th Light Dragoons, were supporting two guns of Ross’s troop, on high ground above the ravine of the Trabancos river. Just as the Commander-in-Chief came on the scene, a squadron of French cavalry, striking in from the flank, rode at the guns, not apparently seeing the supporting troops. They met and broke the squadron of the 12th Light Dragoons, which came up the hill to intercept them. ‘Some of Marshal Beresford’s staff, seeing this, and conceiving the guns to be in danger, rode up to the retiring squadron calling “Threes about[481]!”’ This unfortunately was heard by the supporting squadron of the 11th, who, imagining the order to be directed to themselves, went about and retired, instead of advancing to relieve their broken comrades above. Therefore the mass of pursuers and pursued from the combat on the flank, came hurtling down on the guns, and on the head-quarters staff just behind them. Wellington and Beresford and their followers were swept away in the rout, and had to draw their swords to defend themselves. Fortunately the misdirected squadron of the 11th soon saw their mistake; they halted and turned, and falling on the scattered and exhausted French dragoons drove them back with great loss; few, it is said, except their chef d’escadron, who showed uncommon gallantry, got away[482]. It was a dangerous moment for the allied army—a chance thrust in the mêlée might have killed or disabled Wellington, and have thrown the command into the hands of Beresford or Stapleton Cotton.
Wellington had no sooner detected the flank movement of Marmont’s infantry towards Alaejos, than he ordered the 4th and Light Divisions to retire towards the Guarena, covered by G. Anson’s brigade, while Bock’s and Le Marchant’s heavy dragoons, farther to the left, drew up in front of the infantry of the turning column, and detained it, retiring, when pressed, by alternate brigades. Marmont’s whole army was now visible, moving on in two long columns, of which the more southern followed the 4th and Light Divisions, in the direction of Torrecilla de la Orden, and tried to come up with their rear, while the other, passing through Alaejos, made by the high-road for Castrillo on the Guarena, where the British reserves were posted.
There was a long bickering fight across the eight miles of rolling ground between the Trabancos and the Guarena, not without some exciting moments for Wellington’s rearguard. After passing Torrecilla de la Orden, and picking up there the 5th Division, which had been waiting as a supporting échelon to cover their southern flank, all the British infantry had to march very hard, for troops diverging from the northern French column got close in upon their right, and, moving parallel with them, bid fair to reach the Guarena first. In the retreat the 4th Division moved on the right, and was therefore most exposed, the Light Division next them, the 5th Division farther south and more distant from the turning column of the French. The cavalry pursuit in the rear of the retreating force was never really dangerous: it was held off by Le Marchant’s Heavy and Anson’s Light Dragoons without any great difficulty, and the 5th and Light Divisions only suffered from some distant shelling by the French horse artillery. But the 4th Division, though covered from the pursuit in their direct rear by Bock’s German squadrons, found a dangerous point about a mile on the near side of the Guarena, where two batteries from the French turning column had galloped forward to a knoll, commanding the ground over which they had to pass, and opened a teasing fire upon the flank of the brigades as they marched by. General Cole, however, threw out his divisional battery and all his light companies to form a screen against their attack, and moved on, protected by their fire, without turning from his route. The covering force fell in to the rear when the defiling was over, and the division suffered small loss from its uncomfortable march[483].
Wellington allowed all the three retreating divisions to halt for a moment on the farther side of the stream, at the bottom of the trough in which it runs. ‘The halt near the water, short as it was, gave refreshment and rest to the troops, after a rapid march over an arid country in extremely hot weather[484].’ But it could not be allowed to last for more than a very few minutes, for the pursuing enemy soon appeared in force at several points on the heights above the eastern bank of the Guarena, and many batteries opened successively on the three divisions, who were of necessity compelled to resume their march up the slope to the crest, on their own side of the water. Here they fell into position on Wellington’s chosen defensive fighting-ground, the 4th Division forming the extreme northern section of the battle array, by the village of Castrillo, the Light and 5th Divisions falling in to the line of troops already drawn up in front of Canizal, while the 1st and 7th Divisions were extended to the south, to form the new right wing, and took their place on the heights of Vallesa, above the village and ford of El Olmo.
Some anxious hours had been spent while the retreat was in progress, but Wellington was now safe, with every man concentrated on an excellent position, where he was prepared to accept the defensive battle for which he had been waiting for the last month. It seemed likely at first that his wish might be granted, for the French made a vigorous attack upon his left wing, almost before it had got settled down into its appointed ground. It would appear that General Clausel, who commanded the more northerly of the two great columns in which the French army was advancing (while Marmont himself was with the other), thought that he saw his chance of carrying the heights above Castrillo and turning the allied left, if he attacked at once, before the 4th Division had been granted time to array itself at leisure. Accordingly, without wasting time by sending to ask permission from his chief, he directed a brigade of dragoons to outflank Cole’s left by crossing the Guarena down-stream, while Brennier’s division passed it at Castrillo and assailed the front of the 4th Division. Clausel’s own division advanced in support of Brennier’s.