If you put five economists in a room and ask a question, you'll get seven definitive answers. The IMF seems to have covered all its bases by suggesting ever more stimulus for America, a little stimulus for the UK and austerity for PIGS.
Three economists on Newsnight debated the merits of Keynesian economics. The New Deal got its usual airing. What surprised was that they never seemed to point out that all the major combatants of world war two had a different approach to resolving the great depression. And all were cut short before the effects of whether they were a success or a failure could be realistically measured.
The Fascist Germans pursued arms production with a vengeance, but needed to have an export market to obtain the hard currency to buy the missing rubber, steel, copper and oil to feed the factories. So Germany's pre war boom was accompanied by frequent busts as it struggled to balance its economy. Germany funded its boom with a mixture of taxation, confiscation, restriction and promises. The Mefo bills his 12 billion RM of debt. Unemployment was tackled by removing women, by benefits for staying at home having children, and Jews and undesirables, by imprisonment and death, from the workforce. What would have happened to Germany if they hadn't embarked on war? The opinions at the time were that it was running such unsustainable spending that it would eventually be unable to continue funding its war machine and the cost of all the arms and armaments that it had created, and just implode. But at the same time Germany's 1930's recovery was seen as a miracle, similar to West Germany's.
The Japanese devalued. Abandoning the gold standard that had trapped them, the Japanese devalued the Yen by about 40% and Japanese exports, especially textiles, soared. Large Japanese stimulus spending was used for large drainage, irrigation, land reclamation. Arms spending was also great of course. The worlds third biggest navy had to come from somewhere. All this was funded by government issued bonds. The government issued bonds to the banks and the banks sold them to private investors. Japan was on a Keynesian road to recovery by 1933. Unfortunately in attempting to control inflation and an overheating economy, the finance minister , Takahashi Korekiyo, cut military spending and so was assassinated by militarist radicals that destroyed the Japanese during the 1930s/40s. It is not known if the Japanese economy could have been deflated successfully without setting off a second recession. It wasn't tried. Military spending followed Germany and went ever upwards. And as all countries found rearmament forced up the price of raw materials, so forced up the costs of rearmaments, so increased inflation..
The British Empire tried austerity. Austerity first was the UK solution. The decision to rejoin the gold standard in 1926 had caused harm to the only slowly recovering export trade. Wages and jobs were cut to make factories more competitive and led to unemployment and the general strike. And from then it just got worse. the Wall Street crash was followed up with government tax rises and wage cuts which just removed purchasing power from the economy and unemployment soared to 3 million at a time when the population was just 50 million and women were not working in many workplaces at all. Coming off the gold standard and trade tariffs with the empire helped, but did not end, the damage done, and the recovery was a very long time in coming. Chancellor Neville Chamberlin was a firm believer in controlling overspending and defending the value of the pound. His limited rearmanent policies had not created the booms experienced in Japan and Germany, but hadn't created the debts either. Great Britain could have not have fought long if it had gone into WW2 with an empty treasury.
Even so, with the stimulus in arms spending from 1938 unemployment still failed to fall significantly in the UK, probably as much of the money went on air defences. The aircraft industry, unlike the navy, requiring fewer, higher skilled, workers.
France tried everything in the late 1930's and failed at all of them. It reversed policies so many times it ended up with debt, austerity, unemployment, giant stimulus spending, frightful unproductivity, devaluation and shortages. France was in a terrible position to try and resist the German arms race, partly from having fallen into the depression last and pursued policies that meant it didn't emerge until last either. In 1936, in France, the Keynesian stimulus was spent on increased wages and social benefits rather than increased output and so caused ever increasing inflation that ate up all of those 1936 wage gains by 1938, without the necessary investment to lead to increased productivity. A reminder of how government spending in the 1970's didn't raise living standards, but actually decreased them through stagflation.
And the USA. The New Deal. Well, we know it worked. Sort of. The slowing of the stimulus spending in 1937 led to a big rise in unemployment. up by around 5% to 20%. The US economy stalled that led the right to complain that all the government spending had done was to push up wages, cause thousands of strikes at a time when workers were desperate for jobs, and lead to too high taxes on business. It all got very acrimonious. But what can't be denied is that stimulus had not ended the great depression of 1929. Even the orders for arms from Britain and France that poured in from 1938 didn't sort the economy. What would have happened if the war had not broken out? Could Roosevelt have just continued priming the pump indefinitely? If any country could, the USA could. But would it have worked? Or would each time government spending was reduced, economic measures fall?
World War Two turned all democracies into totalitarian, centralised, bureaucratic economies. Debt and consequences weren't an issue and so the answers to which countries were the most right in ending the depression can't be known.