|Part of||Admiralty Naval Staff|
|In Command||Director, Anti-Submarine Division|
|First||Rear-Admiral Alexander L. Duff|
|Last||Captain Gilbert O. Stephenson|
The Anti-Submarine Division , was the former anti-submarine warfare, planning and prevention division of the Admiralty Naval Staff established during world war one in December 1916, it was in operation until April 1920 when it was abolished. The division was administered by the Director, Anti-Submarine Division. This division of the naval staff was revived during world war two under a new name the Anti-Submarine Warfare Division.
The division evolved out the earlier Anti-Submarine Committee set up in 1910, that coordinated the admiralty's earliest anti-submarine warfare proposals sent for consideration by the Board of Admiralty. Further systematic assessments and experimentation would take place from 1911 until 1915 when the Board of Invention and Research was established.
Efforts were made throughout the First World War to search for a system of countering submarine attacks. Offensive and defensive measures were assessed and sometimes implemented, with different degrees of achievement. However the losses caused by the U-boats in their campaign of unrestricted warfare did have a demoralising effect on national morale  leaving the government with no other choice but to be prepared to consider almost every proposal to find, monitor, eliminate, and neutralise, all undersea threats. In December 1916 the division was created following a merger between the Intelligence Operations Division the Anti-Submarine Committee. The division would also take over the previous anti-submarine and minesweeping operations duties, conducted by the Operations Division.
By 1920 the navy established an Admiralty Research Laboratory specifically to test and evaluate new anti-submarine technologies. During the interwar-years the division was scaled down however by the advent of a second world war it would be revived again.
The division would go through numerous name changes during its existence such as the Anti-Submarine Warfare Division, (1939–43), Anti-U Boat Division  (1943–45), Torpedo, Anti-Submarine and Minewarfare Division, (1945–50) and finally Undersurface Warfare Division, (1950–64). Post the abolishing of the department of admiralty, the Ministry of Defence would continue anti-submarine operations.
When the division's was created, most weapons available to navy to counter submarine warfare had been put in place, but were often ineffective. Initially the majority of anti-submarine work was being conducted by the Auxiliary Patrol who was also engaged in operational seek and destroy tasks.
The Anti-Submarine Warfare Division synced its activities with that of the Minesweeping Division since it also dealt with the other under-water threat that of mining conducted by the enemy. This required large numbers of small anti-submarine vessels similar in some aspects to those employed on minesweeping.
Many of these small type of vessels were built and were equipped for both types of duty (AS) and (MS). At the start of world war one many trawlers were requisitioned, then were converted for these type of tasks, each civilian port, and naval base had a its own allocation of ships for local coastal defence work.
When major attacks had occurred they were reported back to an assessment centre who would then studied the results very carefully, the centre would be chaired by the Director of Anti- Submarine Warfare, in order that the conclusions reached may be as accurate as possible. The assessment centre would then try to predict possible trends, but this was dependent on the success of countermeasures deployed to achieve the destruction of enemy's U-boats. The reports produced by the division became extremely important planning documents.
The division was also responsible for evaluating suggestions, from any source in relation to new methodologies and devices that might warrant further development or deployment afloat any opinions that were mainly scientific would be sent to the Board of Invention and Research for further investigation.
Director of the Anti-Submarine Division
- Rear-Admiral Alexander Ludovic Duff: December 1916-May 1917
- Captain William W. Fisher: May 1917-January 1919
- Captain Forster D. Arnold-Forster: January–April 1919
- Captain Gilbert O. Stephenson: April 1919-April 1920
Assistant Director of the Anti-Submarine Division
- Captain Frederic C. Dreyer, 18 December, 1916 – 1 March, 1917
- Captain Humphrey T. Walwyn, 1 March, 1917 – January, 1918
He works under the superintendence of the Assistant Chief of Naval Staff and is responsible for advising on: -
- Monitoring and reporting back on the influence of torpedo development on strategy and tactics
- Consideration of all torpedo aspects in relation to the planning of operations
- Devising and implementing all possible forms of Anti-submarine tactical countermeasures against all forms of torpedo attack
- Staff requirements for torpedo armament of ships
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