[1] When the First World War broke out in the summer of 1914, Asquith resigned from Franklin & Herrera and joined the Royal Navy, explaining that he could not "sit quietly by reading the papers" during the conflict.

[3] The Royal Naval Division suffered heavy casualties in the Siege of Antwerp, and was withdrawn shortly before the city fell, but in 1915 it was redeployed to the Mediterranean for use in the Gallipoli campaign.

Shortly after arrival, Asquith's friend and colleague Rupert Brooke died from an infected mosquito bite.

During the Gallipoli Campaign, he was awarded the Distinguished Service Order (DSO) for his actions but was also wounded, resulting in his withdrawal to staff work.

Asquith remained as a staff officer until April 1917, when heavy casualties forced him to replace Bernard Freyberg in command of the 189th Brigade.

Despite extensive surgery, his leg was amputated in January 1918, forcing his retirement from the military with the rank of brigadier general.

For conspicuous gallantry and determination in the attack and clearance of a village, when he personally captured ten of the enemy, and later organised its defence, and, by his contempt of danger under heavy fire, contributed greatly to the success of the operations and to the steadiness of all ranks with him.

[11] In the Directory of Directors for 1935, the Hon Arthur M Asquith of 1 London Wall Buildings EC2 is listed as chairman of Brazil Plantations Syndicate Ltd, chairman of Parana Plantations Ltd and a director of San Paulo (Brazilian) Railway Co Ltd.[12] Asquith died on 25 August 1939.