I think that you're both right and wrong regarding the conflicts that you mentioned. Many people chose not to read the signs of impending war....maybe they did not want to frighten their own people or the markets. In the case of democracies, the process of preparing a people and engaging an economy for a war (usually a defensive war) takes much longer, because you need to try and bring public opinion with you in order to gain the maximum support for the war effort. It is very difficult to convince a civilian population, years in advance of a conflict, that a higher proportion of GDP needs to be diverted to the military. In all the cases stated, siren voices, such as Churchill in the UK, warned of the necessity to upgrade military capabilities. The same happened in the US, though given the isolationist stance of the US regime and an economy that had still not fully recovered from the Depression, a minimalist approach was adopted.
The roots of WW I go back to the 19th century.....the naval rivalry between Britain and Germany based on defending their sea routes (resources), various military alliances and the struggle for supremacy in the Balkans between Austria-Hungary and Russia. The murders in Sarajevo lit the spark, but each of the great powers has it's military strategies well worked out down to the train timetabling for troop movements. At least a decade had been spent preparing for a major conflict between the upper echelons within these powers and once the spark was lit, things moves inexorably along their preordained course. Somebody could have shouted stop and many socialist politicians in different countries did, but fear won the day......the fear that if one did not act first and gain the advantage of whatever surprise existed, that one would have lost before the thing even started.
WW II in Europe was inevitable once Hitler came to power in Germany and the allies adopted a strategy of appeasement. The French placed their faith in their defensive Maginot line and the British in the Channel. Churchill had warned about the need to rearm, but given the state of their respective economies, they relied on appeasement and allowed Germany gain a large head start in developing it's military capability. Hitler's ambitious plans were published in Mein Kampf about 15 years before the war.....more people should have read the book and taken him seriously when he came to power.
Had the other major powers in Europe mobilized and called his bluff at any point up to the 1938 Munich Agreement, Hitler would have been forced to capitulate and would have suffered a loss of face at home. After Chamberlain said those words following the Munich Agreement, British rearmament started in earnest. (Chamberlain was simply trying to reassure and settle the British public......much like Bertie and Cowan talking about soft landings and the economy being sound.....bullshit only works for so long) German military intelligence indicated that after the summer of 1939, the British and French rearmament programs would gradually erode the military advantage that Germany enjoyed and as Stalin needed a breathing space to recover from the damage that his own paranoia had inflicted on the higher echelons of the Red Army, we again have a military strategy and timetable in place for war.
The roots of the Pacific conflict stretch back to the Japanese invasion of China in 1931 and the economic sanctions against Japan which followed. As these gradually started to impact more severly on Japan, a clash between Japan and the US became inevitable there too. Even though Pearl Harbour was a lightning strike out of the blue, a lot of diplomatic activity had preceded it and the US War Department was aware that the Japanese Imperial Fleet had put to sea.
So I dont believe that there were any surprises for those in the know.....only for those who were intentionally kept in the dark......and maybe for their own good in many cases. If for example, a rumour gained credence that some foreign army were about to invade us, watch what would happen on the stock exchange and at banks and supermarkets.
The surprised factor is even more difficult to achieve nowadays, given satellite technology, the greater abilities of intelligence gathering agencies and high-tech world media. The Iranians learned this fact when they were informed that the US and others were aware of their secret Uranium enrichment facilities recently. The best deterrent to war is to bind countries closer together in terms of business and trade, and economically and politically in the case of the EU. Failing that, you have to rely on the old military deterrent, which worked quite well in Europe during the cold war.....because at the end of the day, global superpower conflict is a guaranteed loose-loose situation and everything that has been created would be destroyed....so, no war aims could possibly be achieved in such a conflict....and if you cant achieve your aims through war, that only leaves diplomacy.
Make love, not war..............I never killed a Russian, but I did shag one once.