After defeating the army of Castanos at Madrid on July 29th, Napoleon remained in Madrid for four nights. There was no pursuit of the Spanish and Wellington was allowed time to assemble his army across the French line of communications back to Valladolid. A garrison is established for the Spanish capital and a temporary government is put in place to administer the captured Spanish nation and New Castile province but precious time is taken up tending to the details of running a conquered nation. A new treaty is proposed to the Spanish and British but there is no reply. Finally, on the 1st of August, Marmont's Corps is ordered to begin marching back along the line toward Valladolid. The Marshal is not surprised to report back that the British are in Guadarrama. He is astonished though at the number that are there. 60,000 is perhaps twice what Napoleon had expected to try barring his path. 

The rear of the column, including a division of infantry, a division of cavalry, and Napoleon and his artillery would be following up the next morning and then there should be sufficient forces to push the British aside. Marmont would begin the battle at Guadarrama on the morning of the 2nd and when Napoleon arrived with reinforcements, a victory would be achieved.

The French Emperor was enjoying a breakfast in Madrid though on the 2nd of August, before taking the road to the battle, when word came of 30, 000 Spanish within three miles of the Spanish capital. Everything had suddenly changed.

The Coalition forces had an opportunity here to utterly destroy the Emperor's small army and perhaps capture the Ogre. To be certain, the Spanish forces were the battered remnants of an army that had fought three costly engagements with the French in the past two weeks, but the old Spanish General was not going to let this opportunity pass. He would risk the last of the army on this attack.

1000 hrs: Initial French deployment, looking north from Madrid. Axelle division is half way to Guadarrama and the Chloe Cavalry division prepares to depart along the same road.

The British are deployed in such strength that there is no way that Marmont could seriously consider fighting his way through to Segovia. Marmont deploys to defend his position. He has a single brigade occupy Collado Villalba village and deploys the rest of his corps between woods at Galapagar village. The lake to the northwest of the position and the stream to the northeast would be obstacles to the British advance.

For the British, Crauford's corps is mostly Portuguese but the leading elements are British and they would be directed to join the attack against Collado Villalba. Hamilton is under orders to follow the stream and deploy to assault the French right flank. Wellington has personal command of Moore's veteran division on the far left. This would be the extreme left flank of Wellington's attack.

Initially, Bonaparte and his cavalry made for Guadarrama but the arrival of Castanos' lead elements at 1100 hrs has altered the plan and the French horse is already beginning to deploy to the left of the road.

Palafox is entirely Spanish militia so though initially only a single cavalry division opposes the corps, it is enough to give Castanos grave concern. Palafox is ordered to defend on the left while Quixano will attack Madrid. The French garrison there must be destroyed so that the Capital is retaken. Couriers between Castanos and Wellington take approximately two hours and there is some risk involved in the ride.

1200 hrs. Marmont has an aggressive left wing and it advances confidently against the Portuguese on the British right flank. Collado Villalba falls quickly to a coordinated British assault but otherwise, Wellington's advance is cautious. Moore and his veterans though are in columns and marching wide on the elft.

1230hrs: Galapagar is set alight by British howitzers. The defenders try to extinguish the blaze but would fail to do so and they are obliged to quit the village. The large cgurch and out buildings would continue to burn throughout the dry summer day.

Napoleon has recalled Axelle from the road to Guadarrama and also brings his army's artillery reserve against the Spanish. His plan now is to break Castanos' army and destroy it while Marmont holds up the British. If all goes well for the French, Marmont should be able to retreat to Madrid and, with the Spanish army routed, they will be better positioned to fight a second battle against the British on the following day at Madrid.

Castanos, at this point, receives a message from Wellington that reads simply 'I am engaged at Guadarrama and look to contain the French forces here.' Castanos is alarmed and his reply reflects this.

1400 hrs: On Marmont's left, great success is enjoyed by the single energetic brigade. It would see off two cavalry charges and rout or disperse three Portuguese infantry brigades in its attack. Meanwhile, Wellington's left continues to move into position.

1430 hrs. Finally, the leading brigade of the French attack is obliged to retreat itself back to the defensive positions. They have achieved much glory and Crauford's Corps would be unable to advance again for several hours. The terrain of the battlefield is funnelling the two British corps into a very narrow frontage.

On the far left, Wellington has received Castanos' expressive messages and is hurrying Moore south toward Madrid. He will personally accompany this column and entrusts Hamilton and Crauford to conduct the battle. They are at least two hours from Madrid's battlefield though.

1500 hrs: In the South, Napoleon is launching his two divisions against the Spanish militia with quick and decisive results. There is no significant resistance and Castanos only narrowly escapes being captured by Cuirassiers but the heavy cavalry are too occupied by chasing down routing militia.

1530 hrs: Marmont's line continues to hold but British fire is thinning the French ranks. Hamilton prepares to launch assault columns in the gap to the east of the burning village

1530 hrs: Palafox's command effectively ceases to exist. The artillery would courageously remain to get in some effective fire but the whole of the Spanish army is nearly broken. The French cuirassier would try a charge aganst Quixano's rear but the Spanish regulars would manage to get into square to repulse the veteran French cavalry. 

1600 hrs: Quixano enters Madrid and hurries his columns through the streets to come upon the French defenders from the rear and flank.

1630 hrs: END GAME: Moore has arrived and struck the French artillery from behind, instantly obliging the gunners to abandon the ordnance and flee for their lives. Napoleon orders the tired remnants of his divisions to retreat to Torrijos and then rides with a small entourage to join Marmont at the northern battle.

Marmont's corps is nearly exhausted and their perimeter has shrunk. Still, another attack is launched on the left flank and again, the British are pushed back there. Crauford and Hamilton's corps though are still strong and the British have pushed past the chokepoints and rough terrain. It will be easier for them on the morrow. Marmont has no choice but to join in the general retreat to Torrijos.

It is a significant French defeat. They are obliged to retreat to Torrijos. They are cut off from their base of operations at Valladolid and will likely be pursued by Wellington. Castanos was mauled but he was still, at the end of the day, in control of his capital and could spend the night on the field. The Spanish have reclaimed Madrid and driven Napoleon into the wilderness.