The British response to the Tietsen crisis in August 1939 would have been to send 7 Battleships to Singapore. It was never fleshed out as the pressure of Europe and Danzig being of more importance.
The 1939 'Main Fleet to Singapore' proposal.
The Admiralty initially said it could only spare 2 battleships while the Japanese force would probably compose 9. 1939 dispositions were Channel (2 R Class), Scapa (2 Nelson, 3 R class 2 BC) and Med (3 QE). Presuming the 2 come from the Med fleet, probably Malaya and Barham, leaving Warspite behind. When just 2 ships was objected to, then this was lifted to 7 ships by transferring the whole Med fleet (3 QE's) and 4 Home fleet ships. This was advised against as so many ships were in refit (Renown, QE and Valiant) and the intentions of Italy were in doubt. Perhaps the other 4 would be Hood, Repulse, Rodney and Nelson. GB would be unable to lift the blockade of Tientsen (port closest to Peking) and probably lose Hong Kong (hold for 30 days) but Japan would be unable to take on this GB Force in the South China Sea without the benefit of French Indochinese bases. A carrier strike would be possible, IIRC HMS Eagle approached within 100 miles of Singapore undetected during exercises in 1938?
Other ships to add probably cover 1 CV, 4 CA, 2 CL, 24 DD 15 SS from Med Fleet while 3 CL were India based and 1 CV, 3 CA, 1 CL, 8 DD and 18 SS were the China station. 2 CV, 7 CA, 6 CL, 32 DD and 32 SS total. There was also the RAN of 2CA, 3CL, 5DD.
Apparently ranking the Japanese as 'Italian' comes from a 1939! memo that described 6 refitted RN ships (QE, Valiant etc.) equal to Japan's 9 older ships. This was used in justifying the smaller fleet to Singapore. By late 1939, Japan was reeling from the losses in Mongolia, repudiation of the 1911 US trade treaty and the surprise German-Soviet non-aggression pact but GB had lost face in backing down over the Tientsen affair.
The land/air forces were judged to be sufficient at the time in 1941 as:
- they were being built up.
- the oil embargo will have an impact.
- the American's MAY assist.
- the Japanese capabilities were unknown but probably on par with Italy who in 18 months had shown:
- would take advantage of the French surrender
- could be beaten on the ground in North Africa
- could be beaten by the Greeks
- could be beaten at sea
- could only win with help from the Germans.
The Japanese:
- were already involved in a war in China
- could be beaten by Russians
- running out of oil
- could not be helped by the Germans.
Only the navy was an unknown. With the other evidence, and entrenched prejudice coupled with starting to believe our own propaganda, why would the IJN+air forces be any more effective than the Italian Navy had been upto late 1941?
It still took the Japanese 70 days to take Singapore. They would have failed had it come to street-to-street fighting.
Later events showed they should have been saying 'nice doggie' in the second half of 1941 because GB's rock wasn't big enough.