Question: Where was the British World War I division formed that contained the 1st Life Guards regiment ?

text: British cavalry during the First World War
British cavalry regiments , brigades , and divisions

The British cavalry were the first British Army units to see action during the First World War. Captain Hornby of the 4th (Royal Irish) Dragoon Guards is reputed to have been the first British soldier to kill a German soldier, using his sword, and Drummer Edward Thomas of the same regiment is reputed to have fired the first British shot shortly after 06:30 on 22 August 1914, near the Belgian village of Casteau. The following Battle of Mons was the first engagement fought by British soldiers in Western Europe since the Battle of Waterloo, ninety-nine years earlier. In the first year of the war in France nine cavalry brigades were formed for three British cavalry divisions. Other regiments served in six brigades of the two British Indian Army cavalry divisions that were formed for service on the Western Front. Three regiments also fought in the campaign in Mesopotamia, the only other theatre of the First World War where British cavalry served. The doctrine of the British cavalry had been highly influenced by their experiences in the Second Boer War fifteen years earlier, during which one commander had preferred using irregular units to the professional cavalry regiments. By necessity, cavalry doctrine had changed since then, with emphasis being placed on dismounted firepower and covering fire from the flanks, using machine guns and attached artillery, to support cavalry charges. Cavalrymen dominated the higher command positions within the British Army during the war. The only officers to command the British Expeditionary Force on the Western Front were both cavalrymen, while the original commander of the British Cavalry Division went on to command the Egyptian Expeditionary Force during the Palestine Campaign, and another cavalryman became the Chief of the Imperial General Staff. Altogether on the Western Front, five of the ten officers who commanded the five British armies were provided by the cavalry, while another ten commanded corps, and twenty-seven served as divisional commanders. Among other decorations for their valour, eight cavalrymen were awarded the Victoria Cross, Britain's highest award for bravery in the face of the enemy.
Regiment Brigade Division
1st Life Guards 7th Cavalry Brigade 3rd Cavalry Division
2nd Life Guards 7th Cavalry Brigade 3rd Cavalry Division
Royal Horse Guards 7th Cavalry Brigade 8th Cavalry Brigade 3rd Cavalry Division
Household Cavalry Composite Regiment 4th Cavalry Brigade 2nd Cavalry Division
1st ( King 's ) Dragoon Guards 8th ( Lucknow ) Cavalry Brigade 1st Indian Cavalry Division
2nd Dragoon Guards ( Queen 's Bays ) 1st Cavalry Brigade 1st Cavalry Division
3rd ( Prince Of Wales 's ) Dragoon Guards 6th Cavalry Brigade 3rd Cavalry Division
4th ( Royal Irish ) Dragoon Guards 2nd Cavalry Brigade 1st Cavalry Division
5th ( Princess Charlotte of Wales 's ) Dragoon Guards 1st Cavalry Brigade 1st Cavalry Division
6th Dragoon Guards ( Carabiniers ) 4th Cavalry Brigade 2nd Cavalry Division
7th ( Princess Royal 's ) Dragoon Guards 9th ( Secunderabad ) Cavalry Brigade 7th Cavalry Brigade 2nd Indian Cavalry Division 3rd Cavalry Division
1st ( Royal ) Dragoons 6th Cavalry Brigade 3rd Cavalry Division
2nd Dragoons ( Royal Scots Greys ) 5th Cavalry Brigade 2nd Cavalry Division
3rd ( King 's Own ) Hussars 4th Cavalry Brigade 2nd Cavalry Division
4th ( Queen 's Own ) Hussars 3rd Cavalry Brigade 2nd Cavalry Division
5th ( Royal Irish ) Lancers 3rd Cavalry Brigade 2nd Cavalry Division
6th ( Inniskilling ) Dragoons 5th ( Mhow ) Cavalry Brigade 7th Cavalry Brigade 1st Indian Cavalry Division 2nd Indian Cavalry Division 3rd Cavalry Division
7th ( Queen 's Own ) Hussars 11th Indian Cavalry Brigade Mesopotamia Cavalry Division
8th ( King 's Royal Irish ) Hussars 3rd ( Ambala ) Cavalry Brigade 9th Cavalry Brigade 2nd Indian Cavalry Division 1st Cavalry Division
9th ( Queen 's Royal ) Lancers 2nd Cavalry Brigade 1st Cavalry Division