Could the start date of World War 2 been changed?

[uk 75]

Some historians now date the start of World War 2 to Japan's invasion of China. One might also add Italy's invasion of Abyssinia (Ethiopia).
How early or late could the UK and France on the one hand or the US on the other have entered World War 2 and what implications would the change have had on defence projects?
A more decisive British response to Italy's Abyssinia aggression might have served notice on Germany that the democracies were not a pushover.
US entry into WW2 is pretty much determined by Japan's attack on Pearl Harbor and Germany's declaration of war. The strong sentiment for isolationism in US politics does not give much scope for US action earlier.
A British government without Churchill around might have found ways to do another Munich in 1939 or get out of the war in 1940. Japan, however, would still have captured Singapore and Malaya as well as Hong Kong at some point.

 

[Apophenia]

Even before the creation of the Third Reich, Germany was violating the terms of both Versailles and Locarno. Any of those violations could have been casus belli. But neither popular no political will existed for war.

Perhaps a related question might be: How early could Britain and France have intervened to prevent (or delay) the outbreak of WW2? I would argue that the last plausible date is 07 March 1936 - when the Wehrmacht entered the Rhineland.

There were plenty of warnings. Members of the German military had sworn the Führereid in August 1934 before the Reichswehr itself was disbanded in March 1935. The establishment of the Wehrmacht alone violated the peace treaties. What is not clear to me is whether departments of the UK's Directorate of Military Intelligence had any real inkling of just what a 'paper tiger' the Wehrmacht was in 1936.

Present-day discussions of this era usually focus on the Allies' lack of preparedness. But, in reality, the French and British militaries of 1936 were far better-equipped than the 1-year-old Wehrmacht. The occupation of the Rhineland had ended in 1930 but it had been due to end in June 1935 anyway. However, those repeated German violations of the peace treaties meant that Britain and France were no longer bound by the terms of Versailles either.

Had a Franco-British force re-occupied the Rhineland earlier in 1936, Berlin would have had no choice but to back down (at least for a time). It is worth remembering that France and Britain had some rather improbable potential allies at that point too. The Franco-Soviet Treaty of Mutual Assistance was due to be ratified just as the Germans marched back into the Rhineland. And the Stresa Front was, de facto, a Franco-British-Italian alliance aimed at containing Nazi Germany.

I'm not suggesting that the Soviets or Italians could have been relied upon as allies but it does show that both Mussolini and Stalin were worried about German expansion plans. Played well, that could have been useful to Ramsay MacDonald and Flandin/Laval. I'm not sure what Stalin was manoeuvring for but Mussolini wanted to prevent any Anschluß on his northern border. That could have been kept in play (since the West was obviously willing to throw Ethiopia under the bus anyway). Instead, Western powers showed further weakness over the Munich Agreement and dithering over the Spanish Civil War.

Small wonder, then, that the outcomes were the Pact of Steel and Molotov–Ribbentrop Pact.

 

[uk 75]

Britain especially was in the grip of a popular hatred of military activity. The World War of 1914-18 was seen as a disaster brought about by incompetent politicians and fought by equally incompetent generals and admirals.
This found expression in an exaggerated belief in the role of the League of Nations.
France had been castigated by Britain for its occupation of German territory and the Versailles Treaty was widely seen as harsh and Germany hard done by.
Even Churchill took a while to appreciate the danger posed by Hitler but when he did he was seen as an alarmist with form for getting things wrong (Dardanelles, Gold Standard).

 

[uk 75]

The relevance of this thread to weapons development can be summed up in one word: deterrence.
Britain was not rearming to be able to fight potential opponents but to deter them.
This can be seen both in the emphasis on the RAF over the RN and Army.
As Japan emerged as a threat to Britain in the East and Mussolini in the Mediterranean it was keen to avoid adding Germany to the list of naval opponents (the Anglo German naval agreement followed).
The Royal Navy was desperately vulnerable and could not cope with Italy and Japan at the same time.
The combination of deterrence and distaste for the Great War fell hardest on the British Army. Talk of a new British Expeditionary Force (BEF) was banned from Whitehall almost until WW2 broke out.
The crucial role of the United States in defeating Germany in the Great War was the elephant in the room. Chamberlain had a low opinion of Roosevelt and saw US initiatives as wooly minded. Until Churchill arrived in Downing Street relations with Washington were decidedly cool.
Deterrence helped Hitler in particular. Although the Luftwaffe could only bomb Britain once it had bases on the Channel coast the fear of German air raids mesmerised both Baldwin and Chamberlain. This had some positive results, the RAF developed its fighters and radar faster than France.
The way in which the British fought WW2 relied heavily on Bomber Command. The British Army on the other hand needed large injections of US equipment before it could become a serious fighting force.
The Royal Navy also suffered. Its 15 battleships and battle cruisers(our "capital ships") were seen as much more powerful than they actually were. Escort forces and decent aircraft were not provided. It took supplies of US aircraft to make the carriers able to cope with Japan.

 

[zen]

We must grasp the scale of British Intelligence's disastrous merger of two separate foreign 'European' Intelligence operations had during the 20's.

This exposed both operations and resulted in a massive rollup/turning/ revealing of British Intelligence operations.
In Intelligence terms Britain went blind to local conditions throughout Europe and it took a long time to recover.
Arguably that recovery never was achieved as WWII started.