Full list  |  Top Global population: 2.1 billion Olympics: Los Angeles, 1932 (1,332 athletes from 37 nations); Berlin, 1936 (3,963 athletes from 49 nations)

In 1930 Pope Pius XI banned contraception. Thinking chiefly of male prophylactics the Vatican ruling told Catholics it was a grave sin to use condoms that deliberately frustrated the natural power of sex. Preventing natural union was not just a religious flaw. Naval treaties from the 1920s had raised some optimism on preventing war through precise and peacefully agreed to limits on navies. The Washington treaty had placed the UK and US on parity at 525,000 tons, Japan on 315,00 tons and two minor European powers, France and Italy, on 175,000 tons each. But by the 1930s the optimism of the treaty faded fast as signatories gradually discarded its intent – the giant condom had burst – and Japan formally left in 1935. The collapse signalled power players in the world’s oceans were on the whole willing to reproduce more conflict.

The ominous sense of nascent conflict appeared in new publications like the historically detailed Prince Valiant comic strip, first published in 1937 and looking at the mythological past. Between 1931 and 1969 Walt Disney collected thirty-five Oscars. Some were religious. Unemployment by the early 1930s, rocked by productivity improvements arising from mass production lines, reached 2.5 million in the UK, 4.5 million in America and 5.6 million in Germany. As one measure of several radical moves Britain abandoned free trade for the first time since the 1840s. Imposing tariffs on non-Empire goods, later known more simply as imperial preference, was for many an odious betrayal of Anglo-Saxon commercial principles.

Most notably unresolved from the 1920s was the fundamental wrong, and deep miscalculation, underpinning Germany's absence from the High Table of Nations where efficiency and population and location earned her a seat. Sprawling in the void were two key powers like Britain and France, which having Germany had lost her African and Asian colonies in the late 1910s. Colonies lost not to independence or to a more honourable outcome in the Scramble for Africa but to grasping consumption by other imperialists. Britain and France, and to some extent the outwardly anticolonial Americans, kept imperial control over most of the world and rather liked matters that way. Little taste existed for more inclusively and generosity of an enemy they had so earnestly fought and that so earnestly fought back.

Washington DC meanwhile, home to the Fourteen Points and spiritual home of self-determination, took several different paths resting around an instinctive attraction to isolationism. Most important of American exceptionalism was electing President Roosevelt in late 1932. Among several developments this signalled the worlds most passionate capitalist might at least try to wean itself from old habits (Decisive Day #25, 08/11/1932). The Roosevelt administration chased a New Deal throughout the 1930s and beyond into the Second World War, a distinctive shift from the traditional Anglo-Saxon non-intervention that had so far defined the young nation. The afterglow of the New Deal was not eternal. American fascination with big-capitalism and small-government reappeared with force in the 1950s and 1980s. But it was not purely a policy wonk fantasy either. In its way it matched the Soviets Five-Year Plan (1928-1933) that collectivised agriculture regardless of the economic logic. Earlier in the spring of 1931 the Empire State Building opened. Construction started in March of 1930 and it’s height (450 metres, with spire) exceeded a hundred storeys. The pace of construction was a symbol to the country and at one time close to five storeys stacked up each week. ‘The greatest sky scraper ever built’ pioneered a profitable boom in Manhattan property including Met Life, Singer Tower, the Woolworth Tower. The Chrysler tower, with its distinctive decorative spire, arose at a similar time. But the Empire State added its mast. Theoretically this was for airships to dock but this went unused. The only aerial connection, perhaps not as hoped, was when in 1945 a B-25 crashed into the 79th floor and killed fourteen – a curious foretelling of what would happen in 2001. The World Trade Centre, a few street blocks away, took over as the highest New York office tower in 1972.

The colonial powers remained notably keen to secure more trade concessions as China tussled through another civil war; rather more trade than aid a nationalist regime pushing republicanism over Communism. In one memorable turning point the Chinese Communists escaped near certain defeat (Decisive Day #26, 16/10/1934). The implications of the Long March dominated Asia for the rest of the twentieth century. The Communist fascination in China was to some extent odd. During the 1930s famine seeped into dark corners of the Russian empire and order held through only brutality. Malcolm Muggeridge, a British journalist writing of the Ukraine in 1933 said: ‘One particularly remarkable scene I stumbled on by chance at a railway station in the grey early morning; peasants with their hands tied behind them being loaded into cattle trucks at gun point, all so silent and mysterious and horrible in the half-light, like some macabre bullet.’ Khrushchev had caught Stalin’s eyes in the 1930s. ‘We shall totally annihilate the Trotsykites and scatter their ashes to the winds,’ the young leader said in 1937 – perhaps an ironical claim given Khrushchev’s later denouncement of Stalin in 1956 after winning the leadership. But it was one that resonated with the Georgian. Early in 1934 Stalin had openly, if also ironically, claimed admiration for Hitler after the Night of the Long Knives of 1934. ‘Good chap that Hitler!’ Stalin directed a nervous inner circle. ‘He showed how to deal with political opponents.’

Regardless of failures to inhibit reproduction or the consuming hostility of Soviet planned economies addiction to imperial presence explains the implausible optimism inside many capitals of Europe and elsewhere. Humans could not be so stupid twice over. Or could they? The world’s most industrialized and, so many still claimed, most advanced continent may have thrown themselves into a massive war in the 1910s. Unfortunate, yes, but to repeat the folly would surely look like crass carelessness. Surely not again? Surely cooler heads would dodge another massive war? One reflection to this hope-above-reality thinking came in January 30, 1933, saw the son of an Austrian customs official, a decorated corporal from the trenches of World War One, appointed as German Chancellor. Following misses of, first, Versailles in 1919 and Locarno in 1925. The National Socialists commanded by Hitler formed a timely alliance with Conservative Franz von Papen who many expected could moderate Hitler’s more galling policies. President Paul von Hindenberg also shared optimism but already aged eighty there was not much to play for. Hindenburg, great military leader, felt uninspired by the former non-commissioned officer. On first hearing the Bohemian Corporal would be chancellor he asked: ‘That man for Chancellor? I’ll make him postmaster and he can lick stamps with my head on them.’ Only assurances that Hitler was pliant – von Papen the former vice-Chancellor of the Weimar Republic dismissed Hitler as merely ‘hired for our act’ – kept the erstwhile leader quiet. Doubts whether Hitler was a bystander or the contender expired.

In 1933 the Oxford Debating Union, occasional bell-weather of liberal British political opinion, decided it would ‘refuse in any circumstances to fight for King and Country.’ Pacifist passions hovered ever more possessively around British elites for much of the decades. Such a climate encouraged hopes for some American bullet that might fill the breach of the antiauthoritarian barrel. A popular book of 1938 – ‘England Expects Every American To Do His Duty’ by Quincy Howe – captured the spirit of isolationist America. (Decisive Day #27, 08/08/1936) here>>

From deep inside this union of optimism and pessimism appeared the Munich agreement (Decisive Day #28, 30/09/1938). This embodied the hope there would be something suitably big enough short of war to satisfy Nazi Germany and Adolf Hitler. Germany might still not be welcome back at the High Table but this was surely enough good eating to keep them quiet while Britain and France continued their colonial consumption.

On November 25 in 1936 Germany and Japan signed a treaty to safeguard their common interests. One obvious target of the alliance was Russia and with this east-west try to limit the power of the Russian bear the world at war took a decisive turn. Before this day there remained faint prospects that Europe might just dodge another war or perhaps only endure conflict in isolated parts of the troublesome continent. Lurking inside this hope was that Germany felt inhibited by its biggest eastern neighbour. But with the Russian bear awakened and stirring in the military mix there were few if any prospects of Germany projecting power much further than Warsaw. Projecting power into the precious Ukraine seemed outright impossible. Japan massively changed this balance by implying Russia would face two fronts simultaneously from the west and the east. The anti-Soviet optimism received a fillip in 1941. Added to the big three of Germany and Italy in Europe and Japan in Asia came nearly a dozen more signatories. Prominent among this axis of powers were Spain and Bulgaria in Europe and Japan’s puppet state in China.

David Lloyd George worried during the negotiations over Versailles in 1919: ‘You may strip Germany of her colonies, reduce her armaments to a mere police force and her navy to that of a fifth-rate power; all the same in the end if she feels that she has been unjustly treated in the peace of 1919 she will find means of exacting retribution from her conquerors.’ Plenty warmed to this thinking. Marshall Foch looked on Versailles not has a peace treaty but as an armistice for twenty years. Lord Curzon, foreign secretary in 1921, decided that an effective British policy should seek ‘the reestablishment of Germany as a stable state in Europe. Any idea of obliterating Germany from the comity of nations or treating her as an outcast is not only ridiculous but insane.’

But near-sighted triumphed over far-sighted. Already the storm clouds gathered more ominously. Speaking at the League of Nations in 1936 against Italian aggression of Abyssinia Haile Selassie commented ‘It is us today. It will be you tomorrow.’ By 1936 the League of Nations had dithered and slithered into impotence. The French Prime Minister Blum felt bold enough to announce its death in the summer of 1936: “The League of Nations no longer condemns the fascist acts of aggression; the League ‘notes’, the League ‘does this and this’, the League ‘deplores’ – the League make a hypocritical show of balancing between the criminal and the victim. Even more intolerable are the lies concealed in these formulae, and what can be read between the lines: the League’s confession of impotence, its abject surrender, its acceptance of the fait accompli.”

In this dreamy world the Crystal Night that slaughtered Jews on a systematic scale for the first time was simply an accident, no more than an odd German flash in the plan. It was not a warning of future genocide (Decisive Day #29, 09/11/1938). In reality it was anything but an accident to file under ignore. For those with clearer heads it revealed a nascent and systematic Nazi killing machine. Despite everything African-American Jesse Owens defeat of Nazi athletes at the Berlin Olympics showed there was reason and tolerance inside Nazism. There was no pressing worries on racial superiority in Germany or, through this, to budget or build for war. There was Franco's victory in the Spanish Civil War which would surely sop up the last Fascist hostility (Decisive Day #30, 01/04/1939).

Several advances changed lives. Telephony became widespread. Directory enquiries grew across the industrilaised world, public telephone boxes appeared for the first time in 1935, and in 1936 Britain secured the first speaking clock – simply dial up and check your timepiece. Short and memorable emergency 999 numbers appeared for the first time in 1937 and many countries around the world copied them. Chief of the seminal scientific moments, though, was the first jet plane flown by the German Luftwaffe in the summer of 1939 (Decisive Day #31, 27/08/1939) was peaceful advances. Not something that caused a more efficient prosecution of war. Instead they would create more advanced societies where war would take third or even fourth place against economic and technological advances. Hindenburg airship crashed on May 6, 1937. Based on more flammable hydrogen gas than the less flammable helium gas this made ten crosses of the Atlantic in 1936. The time was under 60 hours. Named for Paul von Hindenburg, the former President of Germany, its crashes appeared on television and radio to a wide audience. Fully a third of those aboard died. Other military crashes with less prominent media coverage included the USS Shenandoah in a thunderstorm in 1925, the USS Akron near the New Jersey coast in 1933, and the USS Macon in California in 1935. Britain scrapped their airship programme after losing R101 in 1933 over France, on the way to India at the time.

All such optimism ended when the Nazis blitzkrieged Poland one chilly autumn day in 1939 (Decisive Day #32, 01/09/1939). The pretence, the hope, the self-belief could no longer contain and indeed the world was back inside a maze which only war could identify the exit. For all the hopeful signs the 1930s were eventually a certain and undistinguished descent into one brutal truth: yes, important players would make sure the world looked equally stupid as it was in the 1910s.

On the final day of the century the advance of science told America of a special energy source that could make much difference in the world. Shortly after this time, and fearing the worst, a prominent physicist called Albert Einstein the Nobel laureate left for America. (Decisive Day #33, 11/10/1939).