In the Great War, he commanded the 12th Battalion of the Middlesex Regiment from June to October 1916, and in November 1916, was awarded a Bar to his DSO.
For his actions taking Thiepval, he was given command of the 18th King George's Own Lancers, Indian Army in October 1916.

As commander of the 12th Middlesex, and later of the 27th Brigade of the 9th (Scottish) Division, Maxwell came to be regarded as one of the finest combat commanders serving in the British Army on the Western Front.
He was an aggressive commander who was also both an original thinker and popular with his men.

Despite his rank, Maxwell was frequently at the front line.
He was killed in action, shot by a German sniper, during the Battle of the Menin Road Ridge on 21 September 1917.
He is buried in Ypres Reservoir Commonwealth War Graves Commission Cemetery.
The gravestone inscription states: "An ideal soldier and a very perfect gentleman beloved by all his men."

His brother, Lieutenant Colonel Eustace Lockhart Maxwell of the 11th King Edward's Own Lancers (Probyn's Horse), was killed on 20 July 1916 during the Battle of the Somme, whilst commanding the 23rd Manchester Regiment.
He is commemorated on the Neuve-Chapelle Indian Memorial.

General Maxwell is commemorated with a plaque in St. Giles Cathedral on the Royal Mile in Edinburgh, Scotland.
Maxwell's medals are now held in the Lord Ashcroft collection after sale at auction.
 His wife, Charlotte Maxwell, published a volume of his edited letters in 1921.
In the Great War, he commanded the 12th Battalion of the Middlesex Regiment from June to October 1916, and in November 1916, was awarded a Bar to his DSO. For his actions taking Thiepval, he was given command of the 18th King George's Own Lancers, Indian Army in October 1916.
As commander of the 12th Middlesex, and later of the 27th Brigade of the 9th (Scottish) Division, Maxwell came to be regarded as one of the finest combat commanders serving in the British Army on the Western Front. He was an aggressive commander who was also both an original thinker and popular with his men.
Despite his rank, Maxwell was frequently at the front line. He was killed in action, shot by a German sniper, during the Battle of the Menin Road Ridge on 21 September 1917. He is buried in Ypres Reservoir Commonwealth War Graves Commission Cemetery. The gravestone inscription states: "An ideal soldier and a very perfect gentleman beloved by all his men."
His brother, Lieutenant Colonel Eustace Lockhart Maxwell of the 11th King Edward's Own Lancers (Probyn's Horse), was killed on 20 July 1916 during the Battle of the Somme, whilst commanding the 23rd Manchester Regiment. He is commemorated on the Neuve-Chapelle Indian Memorial.
General Maxwell is commemorated with a plaque in St. Giles Cathedral on the Royal Mile in Edinburgh, Scotland. Maxwell's medals are now held in the Lord Ashcroft collection after sale at auction.  His wife, Charlotte Maxwell, published a volume of his edited letters in 1921.
Francis Aylmer Maxwell