We can count many causes of World War 2, political and others, but the three root causes of World War 2 were :
For many centuries, the territory of modern Germany was divided between over 300 German-speaking small and independent political units ruled by small absolute princes. Prussia, in eastern Germany, with Berlin its capital city, was one of these many countries.
The Prussian militarism started with Friedrich Wilhelm I, "The soldier king" of Prussia (1713-1740), then a small kingdom around Berlin, and developed for over 200 years, making Prussia one of the most militarist countries in history, "A military that has a state". Prussia was an efficient and strictly disciplined military-oriented state, with a militarist mentality and the world's most effective army. Prussia was initially just a small agricultural state with little resources, but "The soldier king" and his successors, with an impressive combination of merciless iron will and organizational talent, converted it to a modern Sparta. Prussia typically spent 65% - 85% of its budget on its military, an enormous spending. Such a system could be sustained for so long only by a combination of :
Prussia's successful expansionist militarism reached its peak under the leadership of Otto von Bismarck, "The Iron Chancellor", who was its prime minister for 28 years (1862-1890). A great statesman and diplomat, Bismarck's political vision was to unify the many German states to one great country, a German Empire in Prussian domination, by a combined campaign of "Blood and iron" and diplomacy. Bismarck achieved that goal in less than a decade, with a series of wars and diplomatic maneuvers, and dedicated the rest of his long tenure to solidify his great achievement, both by helping to keep Europe in peace, and by keeping Prussia and its Junkers class in power in their new Empire, while skillfully capping calls for democracy.
Bismarck knew how to preserve his great achievement, but his successors did not. In 1914 the peace in Europe collapsed into World War 1. After four years of terrible and futile carnage in both sides, the combined weight of several great powers finally overcame the German military. The German High Command in 1918 did not wait for the collapse, and stopped the war when they realized that they're about to lose, saving the country from further destruction.
As a result of the defeat, monarchy was abolished, the large German military was dismantled, later re-established under very severe limitations of its size and equipment, the exhausted country was required to pay unbearably enormous compensations to the equally exhausted victors, and democracy was established, in the country of people who were taught to strictly obey their superiors, not elect them (there were elections in Germany earlier, but the Reichstag (Congress) had no real authority).
On the surface, the new German republic seemed a different country, a peaceful and disarmed democracy that was no longer a threat to its neighbors, and became a prolific and influential center of modern arts and science.
But under the surface, it was still the Prussian Germany, with the Junkers in power in the civil and military service (including the admired wartime supreme commander as president), with a limited military force, but one that was formed from the finest war veterans and demonstrated great resourcefulness in bypassing the limits dictated by the peace treaty, and the country was in a financial crisis and a political chaos, and many Germans blamed the peace treaty's dictations of their country's troubles, and wanted to restore its national pride and past greatness, which above all meant a desire to restore Germany's military strength.
With all the power of great, long-term, political, social, economical and cultural forces that shape human history, historians are awed by the great role of key individuals, the ability of the right person at the right time and place to deeply affect the direction of history.
When World War 1 ended in a German defeat and the large German military was dismantled, most Germans accepted the new reality and did their best to build their new post-war civilian life, in difficult economic circumstances. For Adolf Hitler, who was a plain soldier in the war (severely wounded twice, decorated twice for bravery in battle), the prospects of new life and career were even less promising.
A high-school dropout who was a poor homeless nomad in Vienna before the war, Hitler was not even a German citizen, he was an Austrian who volunteered to the German military when World War 1 started. He had no family or friends in Germany, no contact with his family in Austria, and a [theoretical] attempt to evaluate his social skills by his relations with his fellow soldiers during the war, or with women, before and after the war, would also suggest a very unpromising future, since Hitler was unpopular in his unit, the other soldiers thought he was weird, and he was very inhibited with regard to women.
From such an unpromising start point, the chance that such a person can rise from so low to becoming an extremely popular and successful political leader, seemed practically impossible, but Hitler did that in just 13 years.
In 1920 he resigned from the army (he was still technically a soldier) to enter politics as the leader of a very tiny unknown extreme right political group, not even a party yet, and in 1933 he was elected the Chancellor of Germany, and quickly abolished democracy, as he said he would, and became a dictator of absolute power.
For Hitler's full biography, read my Adolf Hitler essay. Here I'll describe the unique set of qualities of Hitler's personality, and then explain why without them Hitler, or anyone else, could not lead Germany so fast to a second war, a World War that shook the world and almost drowned it in blood.
In his authoritative book "The Rise and Fall of the Third Reich : A History of Nazi Germany", William L. Shirer writes about Hitler :
"The man who founded the Third Reich, who ruled it ruthlessly and often with uncommon shrewdness, who led it to such dizzy heights and to such sorry end, was a person of undoubted, if evil, genius. It is true that he found in the German people, as centuries of experience had molded them up to that time, a natural instrument which he was able to shape to his own sinister ends. But without Adolf Hitler, who was possessed of a demonic personality, a granite will, uncanny instincts, a cold ruthlessness, a remarkable intellect, a soaring imagination and, until toward the end, an amazing capacity to size up people and situations, there almost certainly would never have been a Third Reich.
It is one of the great examples of the singular and incalculable power of personality in historical life.
To some Germans and, no doubt, to most foreigners it appeared that a charlatan had come to power in Berlin. To the majority of Germans Hitler had, or would shortly assume, the aura of a truly charismatic leader. They were to follow him blindly, as if he possessed a divine judgment, for the next twelve tempestuous years."
Hitler was an exceptional speaker, a demagogue. His speeches might now seem weird or funny, and that's what foreigners thought of him until it was too late, but the effect of Hitler's speeches on his political audience was almost hypnotic. First of all, that's what gave him the leadership of the tiny group that he joined, as the other few members, and others who joined later, quickly realized that their only hope of ever getting anywhere in politics depends on Hitler's gift of speech. Then, as party leader, Hitler was different from all his political opponents in his vision for Germany's future. Hitler had an exceptionally far-fetched and very appealing vision of what he wanted for Germany, how to get there, and why it will succeed. Hitler didn't just promise a better future like politicians do. He promised them the world. He convinced them that it's theirs by natural right and that they have the power to take it for themselves, that they are a "Masters race" of superior people, and he was so convincing that they believed him. By that, Hitler dwarfed all his political opponents, and slowly, year by year, but at an increasing rate, more Germans listened to his message and became supporters. Hitler's words were also backed by brutal street violence. German politics in those years was not just speeches, and Hitler operated, ruthlessly, a private army of 500,000 street gangsters, the S.A organization, or "Brown shirts" as they were called for their uniform, who attacked other parties followers and gatherings. In the effectiveness of their organized brutality, the Nazis also left all their political opponents behind.
Those in power, the leaders of mainstream parties and the widely respected president, saw the danger in Hitler and disliked him, but they kept underestimating him until it was too late, and after the 1933 elections, he overcame all of them in a political negotiation in which they did not realize what he was trying to achieve and why, and so he got what he needed while his political opponents thought that the deal they made with him will keep him under control.
So in 1933 Hitler did the unbelievable and became the prime minister of Germany, and his partner Goering became minister of the Police. The Nazi party was a minority in a coalition government, but Hitler and Goering immediately used the emergency authorities of their new roles, combined with massive street violence that totally ignored the law. But since by then the Nazis were the police, the law meant nothing. Hitler was the law in Germany between January 1933 and his death in 1945.
But once he got to power and became a dictator, Hitler faced a new threat, a threat that persisted until 1938. The German military quickly learned of Hitler's plans for a new war. Feeling responsible for saving Germany from disaster, since it was still so weak militarily, groups of senior officers seriously planned to remove Hitler in a military coup, but Hitler, who needed the Generals for his intended war but did not trust their enthusiasm of him and his plans, always outsmarted them, sometimes very narrowly, until when the war started, the series of German victories made the Generals put these plans aside.
The Generals returned to attempting to remove Hitler when he was losing the war, and in 1944 he survived an assassination attempt by the military by pure luck, when a bomb exploded next to him in a room where he held a meeting.
But even after overcoming his domestic opposition, Hitler still had to face the world outside, the far stronger and increasingly worried European powers, Britain, France, Russia, and Germany's smaller neighbors which were protected by alliances and shared strategic interests with those powers, above all the interest to avoid having a militarist and mighty Germany next door again.
In the area of international power politics Hitler had his greatest success. He was a statesman the world had not seen before, an exceptional poker player who played an incredibly dangerous game and won time after time, a series of amazing victories which time after time convinced the worried Generals to delay their plans to remove him, and further increased his already high popularity at home, making him, for a few years, the most genuinely popular dictator in history, which is why the Germans kept following him later, like a losing but still hopeful gambler, all the way down to disaster.
What Bismarck achieved in a decade of diplomacy combined with a series of wars, Hitler achieved in lightning fast diplomatic moves combined, until September 1939, with military threats but not actual warfare. Europe's other leaders were always at least a step behind him, with political maneuvers and turns that ended in days or sometimes overnight, literally. It was unprecedented in diplomatic history, and Hitler managed, with incredible skill and astonishing success, using all the characteristics of his unique personality described above, to arrange and initiate a series of crises on the brink of war, and come out the winner with great gains, territorial and other, time and again, and without actually starting a war, a war which until 1939 he was going to lose because the German military was still too small and ill-equipped to win.
The German Generals knew it well and were rightfully worried, the European leaders knew it, and Hitler knew it, and still, time after time, between 1935 and 1939, he won with weaker cards, thanks to his exceptional personal abilities in a fast paced diplomatic game of threats and negotiations, of alternating between reason and fury, of deception, temptation, intimidation, lies, stress. Just like his former domestic political opponents, most of whom were dead or imprisoned by then, Europe's political leaders also underestimated and misjudged Hitler, and many of them also ended up dead or imprisoned by him, sometimes not much later after meeting him as peers.
But having to deal with a talented diplomatic opponent like Adolf Hitler can not be accepted as an excuse for the political leaderships of France and Great Britain, which could easily put an end to Hitler's dangerous game before 1939, when he still lacked the military power to survive active resistance to his actions, a resistance that was likely to quickly knock him down, either by military defeat or by a military coup.
The appeasement of Hitler, by Britain and France mostly, was not just the result of the incompetence and pacifism of particular top politicians like Neville Chamberlain in Britain, and Edouard Daladier, Paul Reynaud, Georges Bonnet in France. These elected leaders represented the nationwide pacifism of their war-traumatized nations, which resulted from the enormous and futile carnage in the battlefields of World War I, that ended in 1918 and was therefore still firmly in the memories and thoughts of all adults.
The blindness that led to the continued and repeated appeasement of Hitler in crisis after crisis, all of which he initiated, was the result of two logical flaws in the thinking and decision making of the British and French political leaders, and also, which is even worse, in the thinking of the top Generals, mostly of the French military. Since these were logical flaws, they are inexcusable, as political and military leaders have the responsibility to make decisions based on reality, even if unpleasant one, not on single-sided desires and wishes. Furthermore, they were repeatedly warned, by Winston Churchill and others, and even by high ranking members of the anti-Nazi opposition in the German military and foreign office, but all warnings were dismissed until it was too late.
The two logical flaws in the British and French national thought were:
Based on these two unchallenged false assumptions, Britain and France greatly reduced their military manpower and largely neglected military modernization and military technology development, and persisted with that policy even when they knew that Hitler's Germany, like 18th century Prussia, was making a maximum national effort to build the strongest and most technologically advanced military force, in a total violation of the 1919 peace treaty.
By that, these nations' military forces were gradually reduced from a decisive superiority over the small post-war German military, to an increasing inferiority, technological, tactical, and professional. Britain and France made these assumptions false by their own unilateral action and in-action that was based on these assumptions.
The British military establishment was finally alarmed in 1938 and hurried to start closing the gap as they could in the months left before war finally started in 1939. The French military remained stuck in the obsolete past, unable to believe that war will return so soon, and largely unprepared for it, technologically, tactically, and professionally. The few warning voices within the French military, like that of Colonel Charles De Gaulle, were suppressed and dismissed until it was too late.
The British and French leaders and their military, diplomatic, and intelligence advisors should all have known or at least suspect that this was not so, and act accordingly. Hitler made no secret of his long term plans and intentions. He clearly warned the world of his intentions, both in the book he wrote in 1923, which sold many millions of copies since he became the leader of Germany, and in his many speeches and direct diplomatic threats in all the years since. Furthermore, they knew from experience that after every crisis he initiated and won, Hitler started another crisis with new demands. But all that was ignored and Europe's leaders and diplomats were willing to accept Hitler's deception which time and again claimed that he was making one last justified demand and even willing to make reasonable concessions about it. A total lie, time and again.
The British government finally opened its eyes to the frightening reality in march 1939, when less than six months after Hitler was given part of its ally Czechoslovakia, Hitler swallowed the rest of Czechoslovakia with a threat of immediate invasion to it, and just three days later clearly marked his next target, Poland. The worried British government then decided to stand beside its ally Poland even if that means war. The French government still tried to avoid war even after the war started with Hitler's invasion to their ally Poland, and after the last minute ultimatum to Hitler to stop the invasion was ignored, and unwillingly joined the war only following a British diplomatic pressure to stop hesitating and stand beside it.
The result of the appeasement policy was that Britain and France did nothing more than diplomatically protest when Hitler violated the peace treaty (and later with treaties that he signed), started a major rearmament plan, largely increased military manpower, sent his army to the neutral Saar border region (with clear orders to retreat immediately in case of French military response, but this never came), sent his army to the demilitarized Rhine border region, annexed Austria by combination of political murders and threat of invasion.
When Hitler demanded the strategically important western region of Czechoslovakia, they put unbearable pressure on the Czech government, their ally, to immediately give this territory to Hitler to avoid war that Hitler threatened to start, and still did not act when Hitler swallowed the rest of Czechoslovakia with a threat of immediate invasion. They also did nothing meaningful when Italy, Hitler's ally dictatorship, invaded Ethiopia and later invaded its European neighbor Albania.
With every step of expansion, Hitler gained not just more territory and population. He also got the natural resources in these territories, the industry, and the equipment of the dismantled armies of the nations he swallowed, and the military strength of these nations was removed from the potential order of battle of his future enemies.
Czechoslovakia is a key example. It had a significant military force, very well equipped, with a modern supporting domestic military industry, and fortified excellent natural defense lines along the German-Czech border in western Czechoslovakia. The Czechs wanted to fight for their country and could fight well with their modern military and excellent defenses, and definitely with military help from France and Britain, their allies, but they were betrayed by France and Britain which played Hitler's game and threatened the Czechs that by not surrendering these regions to Hitler as he demanded, they, the Czechs, risk being blamed for starting a war. Under enormous pressure by both allies and enemies, the Czechs gave that land and all the military equipment in it to Hitler and remained almost defenseless, only to be forced to complete their surrender to his next threat of immediate invasion just months later. In addition to the valuable territorial and industrial gain, and to removing a significant military force from his list of enemies without firing a shot, Hitler also gained the entire equipment of the dismantled Czech military. This modern equipment, in plenty, was used by the German military in World War 2, and in the invasion of France, two German armor divisions were using solely Czech tanks, and the Czech military industry was producing plenty more for Hitler's army.
One can not write about the causes of World War 2 without referring to the Japanese militarism, that was very similar to the German militarism, and which put Japan in the hands of militarist leaders with expansionist aggression similar to Hitler's. After all, Japan started the war in East Asia even before Hitler became dictator of Germany, and its militarism was defeated only after Hitler's.
It is my opinion that if the attention and military resources of all the world's other major military powers were not committed to the European war against Hitler's Germany, Japan would have kept its military aggression limited to its never ending war in China, which between and 1931 and 1945 consumed the majority of the resources and attention of the Japanese army and remained Japan's original and main goal. If the USA, Britain, France, Russia were not so busy with Hitler, it is likely that Japan would not have expanded its Chinese war to a rapid and easy conquest of the European colonies in the entire South East Asia, and would not attack the US in the Phillipines and Pearl Harbor, and that even if it had, its success would have been significantly smaller and shorter.