| Force | Description |
| 1st Line Territorial Army | Formed in 1908 as the Territorial Force from Volunteer Battalions. Territorial Army (TA) formations were affiliated with Regular Regiments. Indicates TA formations that existed before 1939. |
| 2nd Line Territorial Army | Territorial Army (TA) formations that were created in 1939 when the Territorial Army was doubled in size. Also existed in the First World War. |
| 3rd Line Territorial Army | Raised in the First World War only. |
| 1st Line Yeomanry | Part-time Cavalry formations - equivalent to the Territorial Army |
| 2nd Line Yeomanry | Yeomanry Formations that were created in 1939 when some of the original Yeomanry Regiments were duplicated |
| Active Citizen Force | Militia Force in South Africa |
| Australian Imperial Force | Formed in 1939 as the 2nd AIF as a volunteer force for service overseas. All units of Battalion size are identified by the prefix "2/" to distinguish them from the 1st AIF of 1914-18. |
| Auxiliary Force (India) | Auxiliary Force (India) |
| Burma Auxiliary Force | Formed in 1937 from Indian Territorial and Auxiliary units when Burma was separated from India. Mainly consisted of British, Anglo-Indians and Anglo-Burmans |
| Burma Military Police | Burma Military Police |
| Burma Territorial Force | Formed in 1937 from Indian Territorial and Auxiliary units when Burma was separated from India. Mainly consisted of Burmese and Karens |
| Canadian Active Service Force | Formed in 1939 for Service overseas. In November 1940, it was redesignated The Canadian Army. |
| Home Defence | British formations raised for service in the United Kingdom only. A few did serve overseas. |
| Indian Military Police | Indian Military Police |
| Indian State Forces | Forces raised by the independent Indian Princely States which were lent to the British during times of war |
| Indian Territorial Force | The Indian Equivalent to the Territorial Army |
| Militia | Part-time Units in the Commonwealth outside the United Kingdom which were equivalent to the Territorial Army |
| Militia (Inactive) | The British Militia were the historic home defence forces in the United Kingdom. Thet did not become part of the Territorial Force in 1908 and were basically moribund in 1939 and were not raised at all in the Second World War. Included for completeness. |
| National Military Reserve | Home Defence Force in New Zealand which was incorporated into the New Zealand Territorial Force in February 1942 |
| New Army | Raised in the First World War only. |
| New Zealand Expeditionary Force | Formed in 1939 as the 2nd NZEF, a volunteer force for service outside New Zealand. The original NZEF served in the First World War. |
| New Zealand Territorial Force | Formed in 1911 for Home Defence in New Zealand |
| Regular | British and Commonwealth formations which were part of the Regular Army or Permanent Force in 1939 or were created from mainly Regular formations later in the War. |
| Straits Settlements Volunteer Force | Forces raised in Singapore and Malaya by the British Army |
| Supplementary Reserve | Formed in 1924 to provide a reserve of men with specialist skills. Northern Irish formations were part of the Supplementary Reserve as the Territorial Army did not exist in Northern Ireland. |
| Volunteer | Pre-1908 Volunteer Units in the United Kingdom |
| War Formed | British and Commonwealth formations formed during the War. |
| Young Soldier | Young Soldier Battalions were created in 1940 |