In his speech to the Conservative party conference this month, David Cameron looked back with Tory nostalgia to the days of empire: "Britannia didn't rule the waves with armbands on," he pointed out, suggesting that the shadow of health and safety did not hover over Britain's imperial operations when the British were building "a great nation". He urged the nation to revive the spirit that had once allowed Britain to find a new role after the empire's collapse.

Tony Blair had a similar vision. "I value and honour our history enormously," he said in a speech in 1997, but he thought that Britain's empire should be the cause of "neither apology nor hand-wringing"; it should be used to further the country's global influence. And when Britain and France, two old imperial powers that had occupied Libya after 1943, began bombing that country earlier this year, there was much talk in the Middle East of the revival of European imperialism.

Half a century after the end of empire, politicians of all persuasions still feel called upon to remember our imperial past with respect. Yet few pause to notice that the descendants of the empire-builders and of their formerly subject peoples now share the small island whose inhabitants once sailed away to change the face of the world. Considerations of empire today must take account of two imperial traditions: that of the conquered as well as the conquerors. Traditionally, that first tradition has been conspicuous by its absence.

Cameron was right about the armbands. The creation of the British empire caused large portions of the global map to be tinted a rich vermilion, and the colour turned out to be peculiarly appropriate. Britain's empire was established, and maintained for more than two centuries, through bloodshed, violence, brutality, conquest and war. Not a year went by without large numbers of its inhabitants being obliged to suffer for their involuntary participation in the colonial experience. Slavery, famine, prison, battle, murder, extermination – these were their various fates.

Yet the subject peoples of empire did not go quietly into history's goodnight. Underneath the veneer of the official record exists a rather different story. Year in, year out, there was resistance to conquest, and rebellion against occupation, often followed by mutiny and revolt – by individuals, groups, armies and entire peoples. At one time or another, the British seizure of distant lands was hindered, halted and even derailed by the vehemence of local opposition.

A high price was paid by the British involved. Settlers, soldiers, convicts – those people who freshly populated the empire – were often recruited to the imperial cause as a result of the failures of government in the British Isles. These involuntary participants bore the brunt of conquest in faraway continents – death by drowning in ships that never arrived, death at the hands of indigenous peoples who refused to submit, death in foreign battles for which they bore no responsibility, death by cholera and yellow fever, the two great plagues of empire.

Many of these settlers and colonists had been forced out of Scotland, while some had been driven from Ireland, escaping from centuries of continuing oppression and periodic famine. Convicts and political prisoners were sent off to far-off gulags for minor infringements of draconian laws. Soldiers and sailors were press-ganged from the ranks of the unemployed.

Then tragically, and almost overnight, many of the formerly oppressed became themselves, in the colonies, the imperial oppressors. White settlers, in the Americas, in Australia, New Zealand, South Africa, Canada, Rhodesia and Kenya, simply took over land that was not theirs, often slaughtering, and even purposefully exterminating, the local indigenous population as if they were vermin.

The empire was not established, as some of the old histories liked to suggest, in virgin territory. Far from it. In some places that the British seized, they encountered resistance from local people who had lived there for centuries or, in some cases, since time began. In other regions, notably at the end of the 18th century, lands were wrenched out of the hands of other competing colonial powers that had already begun their self-imposed task of settlement. The British, as a result, were often involved in a three-sided contest. Battles for imperial survival had to be fought both with the native inhabitants and with already existing settlers – usually of French or Dutch origin.

None of this has been, during the 60-year post-colonial period since 1947, the generally accepted view of the empire in Britain. The British understandably try to forget that their empire was the fruit of military conquest and of brutal wars involving physical and cultural extermination.

A self-satisfied and largely hegemonic belief survives in Britain that the empire was an imaginative, civilising enterprise, reluctantly undertaken, that brought the benefits of modern society to backward peoples. Indeed it is often suggested that the British empire was something of a model experience, unlike that of the French, the Dutch, the Germans, the Spaniards, the Portuguese – or, of course, the Americans. There is a widespread opinion that the British empire was obtained and maintained with a minimum degree of force and with maximum co-operation from a grateful local population.

This benign, biscuit-tin view of the past is not an understanding of their history that young people in the territories that once made up the empire would now recognise. A myriad revisionist historians have been at work in each individual country producing fresh evidence to suggest that the colonial experience – for those who actually "experienced" it – was just as horrific as the opponents of empire had always maintained that it was, perhaps more so. New generations have been recovering tales of rebellion, repression and resistance that make nonsense of the accepted imperial version of what went on. Focusing on resistance has been a way of challenging not just the traditional, self-satisfied view of empire, but also the customary depiction of the colonised as victims, lacking in agency or political will.

The theme of repression has often been underplayed in traditional accounts. A few particular instances are customarily highlighted – the slaughter after the Indian mutiny in 1857, the massacre at Amritsar in 1919, the crushing of the Jamaican rebellion in 1867. These have been unavoidable tales. Yet the sheer scale and continuity of imperial repression over the years has never been properly laid out and documented.

No colony in their empire gave the British more trouble than the island of Ireland. No subject people proved more rebellious than the Irish. From misty start to unending finish, Irish revolt against colonial rule has been the leitmotif that runs through the entire history of empire, causing problems in Ireland, in England itself, and in the most distant parts of the British globe. The British affected to ignore or forget the Irish dimension to their empire, yet the Irish were always present within it, and wherever they landed and established themselves, they never forgot where they had come from.

The British often perceived the Irish as "savages", and they used Ireland as an experimental laboratory for the other parts of their overseas empire, as a place to ship out settlers from, as well as a territory to practise techniques of repression and control. Entire armies were recruited in Ireland, and officers learned their trade in its peat bogs and among its burning cottages. Some of the great names of British military history – from Wellington and Wolseley to Kitchener and Montgomery – were indelibly associated with Ireland. The particular tradition of armed policing, first patented in Ireland in the 1820s, became the established pattern until the empire's final collapse.

For much of its early history, the British ruled their empire through terror. The colonies were run as a military dictatorship, often under martial law, and the majority of colonial governors were military officers. "Special" courts and courts martial were set up to deal with dissidents, and handed out rough and speedy injustice. Normal judicial procedures were replaced by rule through terror; resistance was crushed, rebellion suffocated. No historical or legal work deals with martial law. It means the absence of law, other than that decreed by a military governor.

Many early campaigns in India in the 18th century were characterised by sepoy disaffection. Britain's harsh treatment of sepoy mutineers at Manjee in 1764, with the order that they should be "shot from guns", was a terrible warning to others not to step out of line. Mutiny, as the British discovered a century later in 1857, was a formidable weapon of resistance at the disposal of the soldiers they had trained. Crushing it through "cannonading", standing the condemned prisoner with his shoulders placed against the muzzle of a cannon, was essential to the maintenance of imperial control. This simple threat helped to keep the sepoys in line throughout most of imperial history.

To defend its empire, to construct its rudimentary systems of communication and transport, and to man its plantation economies, the British used forced labour on a gigantic scale. From the middle of the 18th century until 1834, the use of non-indigenous black slave labour originally shipped from Africa was the rule. Indigenous manpower in many imperial states was also subjected to slave conditions, dragooned into the imperial armies, or forcibly recruited into road gangs – building the primitive communication networks that facilitated the speedy repression of rebellion. When black slavery was abolished in the 1830s, the thirst for labour by the rapacious landowners of empire brought a new type of slavery into existence, dragging workers from India and China to be employed in distant parts of the world, a phenomenon that soon brought its own contradictions and conflicts.

As with other great imperial constructs, the British empire involved vast movements of peoples: armies were switched from one part of the world to another; settlers changed continents and hemispheres; prisoners were sent from country to country; indigenous inhabitants were corralled, driven away into oblivion, or simply rubbed out.

There was nothing historically special about the British empire. Virtually all European countries with sea coasts and navies had embarked on programmes of expansion in the 16th century, trading, fighting and settling in distant parts of the globe. Sometimes, having made some corner of the map their own, they would exchange it for another piece "owned" by another power, and often these exchanges would occur as the byproduct of dynastic marriages. The Spanish and the Portuguese and the Dutch had empires; so too did the French and the Italians, and the Germans and the Belgians. World empire, in the sense of a far-flung operation far from home, was a European development that changed the world over four centuries.

In the British case, wherever they sought to plant their flag, they were met with opposition. In almost every colony they had to fight their way ashore. While they could sometimes count on a handful of friends and allies, they never arrived as welcome guests. The expansion of empire was conducted as a military operation. The initial opposition continued off and on, and in varying forms, in almost every colonial territory until independence. To retain control, the British were obliged to establish systems of oppression on a global scale, ranging from the sophisticated to the brutal. These in turn were to create new outbreaks of revolt.

Over two centuries, this resistance took many forms and had many leaders. Sometimes kings and nobles led the revolts, sometimes priests or slaves. Some have famous names and biographies, others have disappeared almost without trace. Many died violent deaths. Few of them have even a walk-on part in traditional accounts of empire. Many of these forgotten peoples deserve to be resurrected and given the attention they deserve.

The rebellions and resistance of the subject peoples of empire were so extensive that we may eventually come to consider that Britain's imperial experience bears comparison with the exploits of Genghis Khan or Attila the Hun rather than with those of Alexander the Great. The rulers of the empire may one day be perceived to rank with the dictators of the 20th century as the authors of crimes against humanity.

The drive towards the annihilation of dissidents and peoples in 20th-century Europe certainly had precedents in the 19th-century imperial operations in the colonial world, where the elimination of "inferior" peoples was seen by some to be historically inevitable, and where the experience helped in the construction of the racist ideologies that arose subsequently in Europe. Later technologies merely enlarged the scale of what had gone before. As Cameron remarked this month, Britannia did not rule the waves with armbands on.

Richard Gott's new book, Britain's Empire: Resistance, Repression and Revolt, is published by Verso (£25).