It's not on most people's list of anniversaries to remember but it should be. Almost exactly one hundred years ago, the world's first aerial bombing campaign took place – in Libya. In September 1911, desperate for an empire of their own, the Italians invaded. The Ottoman backwater had scarcely mattered to the sultans; for years it had been used chiefly as a place of exile for unfortunate political prisoners. But war propelled Libya into the headlines, the Italians' colonial foray, triggering a chain of events that led inexorably to the first world war.

When the airman Giulio Gavotti dropped four grenades from his Taube monoplane on to the enemy outside Tripoli, little damage was done: indeed the practice of priming and then dropping live bombs by hand was nearly as hazardous to the Italian pilots as it was to the Turkish troops below. Nevertheless, a staff officer, Major Giulio Douhet, had seen enough to formulate the arguments that would make him the century's foremost advocate of war from the skies. A decade later, Douhet argued in his classic study The Command of the Air that the sheer terror induced by mass bombing of civilian targets would shorten conflicts and save lives; outrage was thus misplaced, for total war was humane. The western way of war had been born in the north African desert.

Few remembered the Libyan victims. Indeed, the Italians had gone to war assuming the Arab population would greet them as liberators from the Ottoman yoke. By the time they realised their mistake, it was too late, and they were pinned back to the coast. Faced with a popular insurrection, they retaliated through the deliberate destruction of villages, wells and herds with force. Nearly 100,000 people were interned or deported, and thousands died of disease or malnutrition in labour camps. Italian planes once again bombed the country, this time dropping mustard gas in defiance of the 1925 Geneva protocol.

Finally, the fascist regime declared that the Libyan provinces were to become an integral part of Italy itself. A stroke of the pen turned the inhabitants into strangers in their own land, paving the way for the foundation of a new Roman empire with Italian farmer colonists. The settlers were still streaming in when the second world war turned the country into a new battlefield, littering the desert with mines that were still impeding oil exploration 20 years later.

With Mussolini's defeat in the second world war, the entire story vanished into oblivion. the way so many other small wars fought by would-be civilisers against "savage races" had done. A new set of Great Powers took over before handing the whole problem of Libya's future to the United Nations. Italy resurrected itself as a cold war ally of Britain and America. Postwar Italians condemned fascism's crimes against fellow-Italians, but they forgot about the far worse crimes across the sea. No one else in Europe cared much either But in Libya the long decades of oppression could not be forgotten so easily. The Italians had devastated the old pastoral economy, and depopulated much of the land: the very term Siziliani (many of the settlers had come from Sicily) remained a term of loathing. Memories of anti-colonial resistance helped to legitimise Libya's new British-backed king, Idris, who as head of the Sanusi order had been a figurehead for the struggle against the Italians. But such memories also helped bolster the 27-year-old Colonel Gaddafi when he accused the king of selling out to latter-day imperialism, toppled him in a coup and set up the republic that he continues to rule to this day.

From the very start of the regime, present and past merged as the anti-colonialist Gaddafi ordered British and American air bases to close and kicked out the 20,000 Italians still living in the country, nationalising their property. As his regime became more and more unpopular, so it found new uses in Libya's history of oppression. Even as it razed the monuments of the Sanusi leadership, now seen by regime propagandists as feudal usurpers of a popular nationalist movement, so it sent researchers into the countryside as part of a vast oral history project to collect memories of the guerrilla war and Italian atrocities.

Such moves not only wrapped the regime in the heroic mantle of the anti-Italian jihad, they served geopolitical purposes too. Two years after forcing the Italians to leave, the socialist Gaddafi was inviting Italian corporations back in, turning the former colonial oppressor into Libya's chief European business partner. And when in 2004 he sought new respectability in Europe, Italy became a crucial ally and history was part of the deal: Berlusconi apologized publicly for Italy's past crimes, and in return, Gaddafi promised to keep Italy's unwanted illegal migrants locked up in camps inside Libya. Visiting the country for the signing of the compensation accord in 2009, the ageing colonel posed next to Berlusconi with a photograph prominently pinned to his chest of Omar Mukhtar, a leader of the uprising whom the Italians had hanged in 1931. Buried in the treaty's small print was Libya's commitment in effect to divert much of the compensation money it was getting from Rome back into the pocket of Italian firms.

It is not only in Libya, of course, that the memory of colonial atrocities has provided rhetorical ammunition for nasty post-colonial regimes. The lesson here however concerns Western amnesia rather than Gaddafi's exploitation of the past. For now that western planes are in action once again over Libyan skies, this past has become our past too; indeed it always was. The majority of Libyans may hate Gaddafi and wish him gone as quickly as possible. But they will remember what we have forgotten – that these planes are not the first, that there is a long history of overwhelming western might being deployed on north African shores, and that western power generally comes professing good intentions. If the west wishes today to underline the differences that surely exist between its intervention now and earlier ones, a precondition for persuasiveness is to familiarise ourselves with what we have forgotten, to understand why this history does matter despite everything that the Gaddafis of the world do with it, and will matter more and more the longer the regime hangs on.