Deflection is an ambiguous term in many sources covering the World War I period, especially British ones owing to the twisted etymology of the word.
|When a British source says...||...it means|
|"Gun Deflection"||Lateral Aim-off|
|"Sight Deflection"||Lateral Aim-off|
Torpedo Control Usage
To make matters even worse, when "deflection" is spoken of in the sense of how to set a Torpedo Deflection Sight or similar device, they are generally speaking of the speed-across attributable to only the movement of the target vessel, discounting that attributable to movement of own ship. On this site, you may find that I employ my own term to make this distinction explicit: Torpedo Deflection.