Similarities between the young Hitler and Stalin are alluring. Stalin was from Georgia, far removed from Moscow, while Hitler was born in Braunau am Inn, Austria, and did not even become a German until the 1930s. Their relationships with their parents, early religiosity, failure to complete secondary education and a descent into social exclusion all bear an eerie resemblance.
In respective class photographs they stand in identical poses, aloof on the edge of the class. Like his nemesis, Hitler was beaten almost daily by his father and, perhaps as a result, developed a very strong bond with his mother. Both mothers, rather optimistically, hoped their sons would turn to the cloth. In Hitler's case he was to be a Catholic priest. They both showed huge potential at their religious schools, but became bored and neither finished their secondary education.
His mother's death in 1907, when Hitler was 18, left him an orphan (his hated father having died in the pub five years earlier). He had moved to Vienna at 16 and dreamt of becoming an artist. He failed twice to get into the Academy of Fine Arts and decided to aim for architecture instead. He was obsessed by Wagner, had only one friend and ran out of money. He made ends meet by painting Viennese scenes for tourists. He fell madly in love with a teenager called Stephanie Isak, who he stalked for years but never summoned up the courage to talk to. Having been rejected previously by the Austrian army he begged to be allowed to join the German army in 1914 and became a runner for a Bavarian regiment. He was exposed to considerable danger and showed great courage, winning the Iron Cross. He was injured several times and once blinded during a British poison gas attack.
After his death his sister uttered possibly the greatest understatement of all time, saying she thought it would have been better if he had been an architect.
Robert Mugabe was born in 1924 in Matibiri village, north-west of Salisbury, Southern Rhodesia. His father abandoned the family when Robert was 10. The void was filled to a certain extent by an Irish Jesuit who inspired Robert with stories of struggle and liberation from the British.
He was raised a Roman Catholic and excelled at his studies. He was a solitary boy, avoiding the others. When not at his books he went out by himself to hunt birds. He is perhaps the most highly qualified of our brood of dictators. He went to the University of Fort Hare in South Africa where he met other young firebrands: Julius Nyrere, Kenneth Kaunda and Herbert Chitepo. He travelled the world picking up degrees, including a BSc in economics from the University of London. He returned to Southern Rhodesia in 1960 where he immersed himself in the turbulent world of Marxist resistance to white rule. He was fascinated by the British, developed a passion for cricket and tea drinking and insisted on perfect manners from his children, best demonstrated, according to him, by the Royal Family.
His opposition landed him in prison in 1964 for 10 years where he picked up three more degrees by correspondence, including one, ironically, in "administration" from London. He later asserted that in addition to his seven academic degrees, he possessed a "degree in violence". He continued to organise assassinations, torture and coups against his fellow black nationalists as much as the government of Rhodesia. He was considered so dangerous that the prime minister Ian Smith did not even let him out for the funeral of his son who had died, aged four.
In the 1970s he fought a guerrilla war from Mozambique, and later cemented his hold on the new Zimbabwe with ethnic slaughter and a harrying of any opposition that continues to this day.
Fidel Alejandro Castro Ruz's father was a prosperous Galician expat who had done well in Cuba. He conducted a long affair with a household servant, Lina Ruz Gonzalez.
Fidel, who was born in 1926, took the name Ruz and lived with the stigma of illegitimacy and the trauma of moving from one foster home to another until he was in his late teens.At this point his father annulled his marriage and married Castro's mother, officially acknowledging his fatherhood of their six children. Fidel changed his name from Ruz to Castro.
He was a good student and excelled at sports. He went to a series of boarding schools and finished up at a Jesuit school in Havana in 1945. As a 12-year-old he was sufficiently impressed with the American President Franklin D Roosevelt that he wrote him a letter of admiration in which he called him "a good friend" and asked for a 10-dollar bill.
As a student he became passionately involved with politics, believing that the influence of the United States must be curtailed. This would help to lift vast swathes of the population out of poverty and seize back political control over Cuban affairs for the Cubans. He practised as a lawyer, largely working on behalf of the poor, and married a student from a wealthy family, Mirta Díaz Balart. He dreamt of going into politics and eventually became a candidate for parliament only to see the election cancelled during a coup by General Fulgencio Batista in 1952. Seeing all legal recourse come to nought, Castro decided that revolution was now the only way open to him. His first act of the guerrilla war was an attack on a barracks that resulted in a disastrous defeat. He was imprisoned. On his release two years later in 1955 he fled to Mexico. In December 1956, he and 81 followers invaded Cuba on a yacht. All but around 20 were killed and Castro headed for the mountains to regroup. It was an inauspicious beginning.
Mao was born in 1893, the eldest son of a well-to-do peasant family in Hunan, central China. His father was able to pay for schooling but he was still forced to work hard on the family farm. While not reading romantic historical novels or poring over the great thinkers of China's past, his great hobby was swimming. He served briefly and uneventfully on the side of the revolutionaries in the 1911 uprising that put an end to more than two millennia of imperial rule. After completing school he travelled to Beijing, where he worked as an assistant librarian and attended the university as a part-time student. He was won over by communism and became a founder member of the Chinese Communist Party in 1921, although he may have been influenced as much by the promise of a job and a salary from the Soviet Union as he was by Marxist ideology. Either way it was the beginning of decades of political and military struggles that would only come to an end in 1949. He spurned the traditional communist emphasis on the urban proletariat, spotting correctly that one did not exist in China. He concentrated on the peasants; they would be the backbone of his revolution. He was utterly ruthless. His first wife, whom he had abandoned in Hunan in the early 1930s, was apparently not greatly distressed when his second wife was tortured and killed with their eight-year-old son forced to watch.
Initially Mao and the Communists were allied to the Chinese Nationalists, the Kuomintang, against the warlords who controlled much of China.
Soon, however, the Nationalists turned against the Communists, and in 1934, having been encircled in southern China, Mao led the communists on the "Long March" a 6,000-mile journey to establish a new base in remote north-west China. There he relentlessly tortured and murdered his way through the top echelons of the Communists and on the outbreak of war with Japan he seemed more concerned with his Chinese enemies than with the Japanese occupiers.
Strikingly, like Hitler and Stalin, Napoleon was from the geographical extremes of the country he would one day rule. Born Napoleone di Buonaparte in the town of Ajaccio in Corsica, on 15 August 1769, it had only been one year since the island was transferred to France by the Republic of Genoa. His family were of minor Italian noble stock and he spoke Italian as a child; only learning French to get into a French military school. He never mastered spelling and, like Stalin, spoke with a thick accent for the rest of his life. His father died when he was only 15 and he took up the burden of supporting his mother and siblings. Little did they know that their brother would one day hand them the crowns of Spain, Holland, Westphalia and Naples. His mother was a towering influence in his life. He would later give her all the credit for his success.
Later propagandists portrayed him as a natural leader at school, with feats such as outflanking enemies in mass snowball fights, but there is no real evidence of this. He was quiet, a loner, teased by wealthier French boys for his accent and background. His teachers judged him a hard worker but "poor at dancing and drawing". Unsurprisingly this was no bar to his entering the artillery, the one arm of Ancien Regime armies where professionalism and qualifications were unequivocally valued. Even there he felt oppressed by rank and hierarchy, and when France broke out in revolution he embraced it wholeheartedly.
Chaos, insurrection and war gave him plenty of opportunity to show off his talents. His rise was meteoric and within a decade he had established himself as one of the greatest military commanders in history.
Saloth Sar, aka "Brother Number One", or "Pol Pot", was born in May 1925 in central Cambodia in a sleepy settlement where wooden houses stand on stilts above the Stung Sen River. His family were prosperous, devout Buddhists with excellent connections; his sister was a concubine of the puppet king. As a result he had a privileged upbringing and attended a series of Catholic schools set up by the French colonial authorities. His brother remembered him as being a "gentle and kind" child.
In 1949, he won a scholarship to study in Paris where he joined the French Communist Party. He failed his exams three years in a row, but ironically this poor academic record enabled him to build a considerable following among the Communists, who were bitterly anti-intellectual and regarded him as a bona fide peasant and thus the key to revolution. In the evening he would hold court in his apartment in the Latin Quarter, enthusing useful idiots and fresh converts with dollops of Marxism and charisma. He returned to Cambodia in 1953 after his scholarship was revoked and became one of the leaders of an underground Communist movement, the Khmer Rouge, although his day job was teaching French literature and history at a new private college. For a man who became infamous for hating foreign-educated intellectuals, urban-dwellers and the privileged, it was an odd choice.
Cambodian independence in 1954 was followed by depressingly familiar post-colonial struggles as nationalists, Communists and everybody else fought over the spoils. Like all his fellow dictators, Pol Pot was supremely confident in his own judgement, utterly ruthless, and enormously charming. He flourished amid the chaos. Reactionary regimes were toppled by coups which left the whole system vulnerable to foreign intervention and rural insurgency.
Dan Snow presents What Britain Earns, a major survey of what we all get paid to do our jobs, at 9pm on 9 January, BBC2Reuse content