The RN had wanted 70 cruisers in the early 30's. They didn't get them due to treaties and lack of money. I believe that was just to counter the Japanese and provide for whatever else may have been going on. In the early 30's Germany was not a real threat, so that the British were looking at numbers to counter Japan with Japan timing the out break of war to have the most ships ready for combat and the RN having the normal number undergoing refit/repair and using some cruisers for trade protection even in the Atlantic while fighting the Japanese.
German and Italian building programs changed the desired numbers as they also became more belligerent.
Japanese (and many others) used search lights at times and the use of star shells was wide spread. Some navies (including the RN) sometimes fitted dedicated star shell guns.
The 70 cruiser requirement can be traced back to 1924 but Friedman notes "Unfortunately no credible explanation has survived, but at times it was stated that twenty-five were for the fleet and forty-five to protect trade". He then deduces from various documents, statements etc that it would look something like this:-
Fleet - 2 squadrons (10 ships) for the scouting line & 2 squadrons (10 ships) to work with the destroyers + 25% margin for refits = 25
Trade protection in various areas:-
China - 2 squadrons
+ single squadrons on the following stations
Australia
New Zealand
Indian Ocean
North Atlantic
South Atlantic
Total - 7 squadrons with 35 ships + 25% margin + flagship for Australia / New Zealand = 45
The China squadrons would have been to hold the fort until the arrival of the Fleet from Britain. Note this was based around 5 ship squadrons but later 4 was the norm. So it is a bit of a moveable feast. And this is not just the RN but also the Dominion navies.
There seems to have been a reluctance by the Admiralty in the 1920s to expressly state that Japan was the "enemy" lest the politicians not see it that way and use it as an excuse to cut the Fleet. And in the mid-1920s Germany & Italy present no credible threat.
By 1935, with escalating threats elsewhere 70 was accepted by the Government as the
minimum acceptable especially since the USA could not be depended to help against Japan. So the outcome of the 1936 London Treaty was a lifting of the quantitative limits on cruiser tonnage and the imposition of a qualitative limit of 8,000 tons. That helped Britain in the search for numbers. From 1936-38 the RN had been ordering 7 cruisers per year with another 4 in 1939.
But in 1937 the RN prepared a document outlining a "New Standard Navy" which set the cruiser requirement at 100 which was to be achieved by 1944. This was nver formally adopted but many of the orders placed match it fairly closely.
On 3 Sept 1939 the British & Commonwealth cruiser fleet looked like this:-
1 WW1 Town class -HMAS Adelaide
13 C class - 6 coverted to or under conversion to AA cruisers (plans for another 4 conversions were cancelled on outbreak of WW2. Intended for convoy protection)
8 D class - (plans for conversion to AA ships cancelled on outbreak of WW2. intended for convoy protection)
2 E class
1 modernised Hawkins - Effingham
2 Hawkins - rearmed on outbreak of WW2. (these had been disarmed around 1936 to comply with the 1930 London Treaty)
7 Kent - 2 RAN manned
4 London
2 Norfolk
York & Exeter
5 Leander - 2 New Zealand manned
4 Arethusa
3 modified Leander - all with the RAN
10 Town class
Total 64 ships.
Under construction or on order with construction about to begin:-
10 Dido
11 Fiji
Then on 4 Sept 1939 plans made immediately pre-war were put into effect. It was decided to complete 2 of the Didos with 4.5" guns intended for the D class conversions in order to obtain them sooner. Another 6 Dido (4 agreed pre-war + 2 to use the 5.25" turrets on order for the 2 ships switched to 4.5") and 2 Fiji (already planned but orders were brought forward) were ordered to utilise available building space. Then on 28 Sept 2 Fijis to be built in Royal Dockyards were cancelled to free up the manpower for conversion and repair work.
On 3 Sept 1939 a number of the older classes had only recently been reactivated following periods in Reserve. Dorsetshire, Kent, Cornwall & Birmingham were on the China station while Manchester, Liverpool & Gloucester were on the East Indies station.
No further cruisers were able to be ordered until 1941 due to changed priorities. Of these only Swiftsure saw combat while HMCS Ontario (ex Minotaur) was en route to the Pacific when the war ended.
