Later in the war, the need for more motor torpedo boats led to guns being removed from some Fairmile Ds and torpedoes being fitted in their place. Both torpedo boats and motor gun boats were needed for coastal coverage around D-Day. Even after conversion, the Dog Boats retained a considerable gun battery because they still needed that firepower. The mixed armament added torpedo capability while preserving much of the D's strength as a motor gun boat.
Notable Point · 1:32-1:57
Fairmile D torpedo conversions and D-Day
Some Dog Boats traded part of their gun armament for torpedoes later in the war while retaining considerable firepower for coastal-force work around D-Day.