“This kind of war was full of fascinating thrills,” Winston Churchill would say. “Nobody expected to be killed.” Thus he described the brutal colonial conflicts of his youth, often against tribes in Africa who were woefully deficient in modern, mechanised instruments of death.

Candice Millard’s Hero of the Empire is a fluent and readable account of Churchill’s early life as a buccaneering, attention-seeking journalist and soldier. It is focused on 1899-1900: the later statesman, with characteristic bombast, declared that this year laid “the foundations of my later life”.

The 24-year old Churchill arrived in South Africa in October 1899 as a correspondent for the Morning Post to report on the second Boer war. He was captured by the Boers but managed to escape to Delagoa Bay, now Maputo Bay in Mozambique, having travelled many miles alone over enemy territory. Later he returned to the Natal front as an officer and, as he recounted, liberated the men with whom he was imprisoned.

He was determined to make a name for himself on the battlefield, and in doing so created a platform from which to enter politics. “There is no ambition I cherish so keenly,” he once confided to his younger brother, Jack, “as to gain a reputation for personal courage.”

The story in Hero of the Empire has been told before, and there isn’t much new that Millard brings to a narrative once as familiar as the tales of Francis Drake and Horatio Nelson – thanks in part to Churchill’s own self-mythologising. To a younger generation, however, the story of Churchill fighting in South Africa is extremely remote. His familiar image is one of the elderly, growling, overweight military leader, brimful of whisky and rhetorical excess.

In contrast to today’s politicians, Churchill’s career is astonishing in its length. The variety of circumstances and events in which he was a major participant can often bewilder. No other figure in any country could have boasted of fighting Cuban rebels against Spanish rule in 1895 (when he developed his taste for cigars) and participating in summit meetings almost 60 years later with the likes of Eisenhower, Truman and Stalin.

Born in 1874, he reached adulthood at the height of the British empire. He never questioned or doubted the nature of Britain’s imperial mission. Hence his remark during the second world war that he had “not become the King’s first minister in order to preside over the liquidation of the British empire”.

Churchill spoke these words in the House of Commons in November 1942. More than 40 years earlier, in the second Boer war, his commitment to empire was just as passionate. He believed in Britain’s destiny to lead the world in political freedom and moral improvement. His wartime speeches achieved their effect precisely because of this heady mix of moralism and supreme confidence in his country’s mission.

The empire was indeed the most constant political cause Churchill espoused. As a young Tory in the 1890s, he was enthused by the legacy of Disraeli’s romantic imperialism. Even after crossing the floor to the Liberals he worked, as first lord of the admiralty, to ensure that the navy was fully equipped and prepared for conflict. As a “die-hard” Tory backbencher in the 1930s, now identified with the right of the Conservative party, he denounced government plans to give India dominion status.

Millard’s book is unusual in the attention it pays to South Africa as the scene of Churchill’s early military adventures. During the second Boer war, as Millard observes, the British promised that, as soon as the Boers were defeated, life for non-whites would change dramatically. The British in South Africa always portrayed themselves as more enlightened and tolerant than the “narrow-minded”, “intolerant” Boers. Millard shows how the British government failed to live up to its stated ideals.

After his return to England in 1900 Churchill was firmly fixed on winning a seat in parliament. He had lost in his first attempt to be elected as the Conservative candidate for Oldham in 1899. His Liberal opponent in the byelection, Walter Runciman, ridiculed Churchill’s previous youthful adventures, saying: “I have not been a swashbuckler around the world.” Churchill replied: “I do not belong to a radical party composed of prigs, prudes and faddists.”

His quick wit was accompanied by a brief attention span. Indeed, Churchill’s critics have often questioned the depth of his knowledge and his intellectual engagement with imperial problems. In the 1900 general election, he contested Oldham again, this time beating Runciman. It was the beginning of a 60-year love affair with parliament. In his opening speech, he spoke fondly of the empire and encouraged his fellow MPs, anxious about the effects of the ongoing war, to think broadly about Britain’s imperial family.

Later in the speech, Churchill stressed the symbiotic relationship between Britain and her colonies, particularly the so-called white dominions. He concluded: “They belong to the empire, and … the empire belongs to them.” As Millard effectively shows, the British empire and Churchill – from his early soldiering days to his apotheosis during the second world war – were also mutually dependent.

• Kwasi Kwarteng’s Ghosts of Empire: Britain’s Legacies in the Modern World is published by Bloomsbury.

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