World War 1 saw nearly 100 men from the City of London Police join either the Army or Navy during the first year of hostilities.
In April 1915 between 300 and 400 men were paraded before the Commissioner, William Nott Bower who invited them to join up. He assured them that service for their country would not affect their promotion opportunities on their return. He also said that when those that remained behind saw their comrades being decorated by the King they would regret not having done their bit.
By Sept 1915 310 members of the Force had joined the Navy and Army. The break down being as follows: –
| Navy and Naval Reserves | 111 |
| Royal Bucks Yeomanry | 30 |
| Royal Horse, Field & Garrison Artillery | 36 |
| Royal Engineers | 8 |
| Household Cavalry | 13 |
| Brigade of Guards | 23 |
| Royal Dragoons | 2 |
| Scots Greys | 1 |
| Various foot regiments | 30 |
| Military Police | 37 |
| Royal Marine Artillery | 4 |
| Army Service Corps | 8 |
| Various Territorial Battalions | 7 |
In his 1915 annual report Nott Bower states that to assist recruitment to the Armed Forces there had been no candidates accepted to the Force since December. 89 pensioners had been allowed to re-join the Force to maintain its efficiency. Of 2,330 Special Constables who had been enrolled, 921 subsequently left to join the Armed Forces, including the Commandant.
Going further to support the dependants of those who had gone to war allowances were made of 15s per week to wives, 2s 6d to each child and 8s to other dependents, all from the Police Fund.
On Sunday 22nd June 1919 at St Botolphs Church Bishopsgate a memorial service was held for the 40 officers of the Force who had lost their lives during the war.
