On the evening of April 1919, General Reginald Dyer ordered a squad of Indian soldiers to open fire on a mostly peaceful crowd of 25,000 men, women and children attending a political rally in the Jallianwala Bagh, a large enclosed public square in the Sikh holy city of Amritsar. After 10-15 minutes of continuous fire, more than 300 lay dead and countless others were wounded. With ammunition running low, Dyer called a ceasefire and led his troops back to barracks, leaving the wounded untended.

Nigel Collett traces the life and military career of Dyer, examining the circumstances leading up to the massacre at Jallianwala Bagh, one of the worst atrocities ever committed by the British on a civilian population. The Butcher of Amritsar also relates the history of British imperialism and the growth of Indian nationalism.

Born in India in 1864, Dyer received his early education at Simla, in the foothills of the Himalaya. The son of a wealthy British brewing family, Dyer and others in trade were scorned as boxwallahs by the class-obsessed British society. He was badly bullied at school, leaving him shy and unable to get along with other people.

At the age of eight, he was sent to school in Ireland, then in the throes of famine and rebellion against the British. After officer training at Sandhurst, Dyer had to spend two years with a home regiment before joining the Indian Army. He first saw action and civil unrest in Belfast in 1886, before being sent to fight in the third Burma war. Burma was an eye-opener for Dyer, where the brutal suppression of the natives by the British imperialists gave him a 'lifelong taste for acting on his own and for avoiding close supervision' that would end in disaster. After a 12-year exile, Dyer returned to India and was reunited with his family. En route, he revealed a darker side to his character when he became involved in a violent brawl with the native crew of a riverboat. The incident indicated 'an inability to prevent his temper turning to violence against native Indians'.

In 1912, after several years of military service with his regiment, the 25th Punjabi Infantry, Dyer was commanding officer when they were ordered to Hong Kong, where the revolution in China was threatening to spill over into the colony. This was a tumultuous time in Hong Kong's history, with the territory in the grip of a bubonic plague epidemic and marked by events including pirate raids on Cheung Chau and Lantau, and the attempted assassination of Governor and Lady Henry May. However fascinating to local readers, the chapter adds little to the story of the massacre at Amritsar, to where the regiment returned in 1915.

German agents in Afghanistan had been trying to foment unrest and insurrection in British India, and the 25th Punjabis were sent to northern Persia to forestall any trouble. Dyer had become convinced that the best way to deal with such revolutionaries was 'to strike swiftly and to strike hard to forestall greater trouble'.

In Persia, Dyer was far from supervision and in his element. However, with the end of the first world war, the Punjab was badly hit by inflation, and new taxes and law reforms sparked civic unrest, particularly in Amritsar. This was also a time of growing Indian nationalism and Gandhi's satyagraha movement, which advocated peaceful resistance to British rule.

On April 10, 1919, conditions in Amritsar had deteriorated, with violent mobs rioting in the streets, and the British had lost control of all the city apart from the military cantonment. The murder of several prominent British citizens prompted the civilian authorities to urge the use of 'full military force' to prevent further unrest. Despite receiving no orders to do so, on April 12, Dyer moved from his regimental headquarters in nearby Jullundur to Amritsar, where he assumed control.

He found the Punjabi capital in uproar after the riots and all communications cut off. To Dyer, Amritsar had become enemy territory and he considered it his duty to defeat and punish its inhabitants at any cost, to impose the law. He promptly imposed a curfew and proclaimed martial law, banning meetings of five or more. Whether the people chose to ignore him or simply didn't hear about the proclamation is unclear, but the rest is history.

Collett has thoroughly researched Dyer's biography and clearly knows India and its history, as he might as a former lieutenant-colonel of a Gurkha regiment. Despite his own military background, the author is fair to Dyer, pointing out condemning and redeeming features alike, ultimately creating the impression that Dyer may simply have been the wrong man in the wrong place at the wrong time.

After the massacre, Dyer went on to fight on the North-West Frontier, before being summoned to England, where the inevitable inquiry into the incident forced him to retire. Dyer's thoughts on the massacre can be summed up by his bitter remark to a reporter who met him on his return to Southampton: 'And now I am told to go for doing my duty - my horrible, dirty duty.'