During the first half of the 20th century, millions of Muslim women decided to abandon the head coverings their mothers had used; in the second half of the century, millions of Muslim women resumed wearing the veil. How and why these fluctuations of personal habit affected so many across the Muslim world is the question Leila Ahmed sets herself. She focuses on Egypt, which was a key influence in both the unveiling and the veiling, to trace the many meanings which this piece of cloth has acquired. It's an acute study of how issues of political power and empire interact with women's own claims to autonomy within families and communities. Ahmed beds her analysis into the wider political currents of Egypt without ever losing sight of women's own interpretations of what they were doing and why.

What adds force to the analysis is the sense that the book has been a journey of personal discovery for Ahmed, a Harvard academic. She grew up in Cairo in the 1940s, and was raised by a generation of women who never wore the veil; she absorbed from them the assumption that the veil was backward, a restriction of female autonomy. Like many Muslim women of her generation, the veil's reappearance has been shocking, unexpected and regarded as a step backwards. Writing the book has forced her to reassess such assumptions, and come to a new, more positive understanding of the veil.

The book starts at the height of British imperialism in the late 19th century when Lord Cromer effectively ruled the protectorate of Egypt. Many of the issues raised in that time have uncanny resonances with the recent debate. In 1899 Qasim Amin published The Liberation of Women, which provoked a furore: he argued that European civilisation was clearly superior to that of Egypt; if women were not veiled in Europe, then it was clearly not necessary. In Ahmed's words, he claimed that "Muslim societies are to be counted as advanced or backward by the extent to which they abandoned their native practices, symbolised by the veil".

Following Amin, huge numbers of Egyptians westernised their furniture, their cities, their houses and their clothing. Amin wanted a profound transformation of Egyptian society: "It is impossible to breed successful men if they do not have mothers capable of raising them to be successful," he wrote, making very clear that liberation of women was a means to achieving a better sort of man. At the heart of Amin's "divided consciousness" as a Europeanised Egyptian was a modernisation strategy for the nation  and veiling was a crucial symbol.

Cromer, on completion of his term in office, boasted that he had "practically abolished" primary education in the country. Yet in a bestselling book he expanded on the inferiority of the "dark-skinned Eastern" and on how Islam degraded women as exemplified by the practice of veiling. He set in train the notion of "saving brown women from brown men" (which, as Ahmed points out, was promoted by both Cherie Blair and Laura Bush ahead of the US invasion of Afghanistan).

For millions of Egyptian women, abandoning the veil was a statement of aspiration to modernity and held out the promise of education and work. It was not related, insists Ahmed, to secularisation; religious women were as likely to go unveiled as the less devout.

What turned this social trend around was the trauma of the Arab-Israeli wars in 1967 and 1973. The humiliating defeats of the Arabs were perceived as a punishment by Allah and led to a renewed religiosity. Meanwhile an alternative idea of modernisation strategy took hold  the Muslim Brotherhood's demand for a more energetic religious practice. As Amin had once done, the Brotherhood called for a profound transformation of Egyptian society; as part of this political project, the veil would again become a central symbol. The clothing advocated by the Brotherhood expressed two key ideas: gender segregation and egalitarian principles of social justice. The veil as a statement of the claim to justice has spread across the world  in the west, against discrimination and an aggressive foreign policy; in the Arab world, against corruption and economic injustice.

But, points out Ahmed, there are much more pragmatic, private reasons for the veil's popularity. Here she draws on a range of fascinating research studies conducted from the 1970s onwards, which paint a picture of women using the veil to resolve tensions between family convention and freedoms such as going to university and working. In crowded buses and lecture theatres, the veil is a "culturally available way" to make a statement about being a good Muslim. "Paradoxically . . . adopting strict Islamic dress" enables women "to flout traditional limits on their autonomy," argues Ahmed, particularly in lower-middle-class families. The majority of women in these studies emphasise that wearing the veil has been a personal decision. Even if there are broad social and political trends shaping these decisions, they end up being experienced by individuals as private emotions.

Egypt provides a much more compelling narrative than America, where Ahmed turns for the last section of the book. The activism of America's 10m-strong Muslim community has a much less significant bearing on the global umma than Egypt. American Muslim community politics bear similar characteristics to those in the UK: some thriving activism alongside complex diaspora factions and new initiatives coming together and petering out. She picks out the more liberal progressive representatives such as Laleh Bakhtiar, the first Muslim American woman translator of the Qur'an, and declares her conclusion to be far more optimistic than she would ever have imagined: she places her faith in the last decade's "tremendous liveliness and activism among American Muslim women". Certainly, it offers an intriguing combination of traditions, but I've seen little evidence that it travels well to Muslim minority communities in Europe, let alone other parts of the Muslim world.

This book is a drawing together of many other scholars' work, in particular that of Gilles Keppel; the political analysis is at times a bit sketchy and economic contexts are largely absent.Perhaps most significant for a western readership is the tart warning that support for Muslim women must be "without aiding and abetting imperial projects". Ahmed is scathing about western concern for women believed to be oppressed by Islam existing alongside an indifference to the very same women when they die at the hands of western aggressors.

Madeleine Bunting's The Plot is published by Granta.

In 1955, the Oxford historian Albert Hourani published an article entitled "The Vanishing Veil", predicting that the centuries-old practice would soon disappear from Muslim societies. Over the previous half-century, women in the eastern Mediterranean Arab countries, led by Egypt, had gradually abandoned their traditional coverings. By the time an isolated nostalgic called out to Gamal Abdel Nasser at a rally in 1962, asking him to reinstate veiling, the Egyptian president could dismiss him with the quip that he had no desire to "engage in battle with 25 million people"  Egypt's population at the time.

More than 50 years later, the many forms of hijab (Islamic veil or covering) are on the rise in both the Muslim world and the west  and so are states' ineffectual attempts to contain them. A law banning face-covering veils from public places has recently come into force in France; Germany has a partial ban on headscarves for teachers; Turkey has banned Islamic coverings from universities; and Syria recently reversed a ban on face veils for primary school teachers. Britain ruled out a proposed "burqa ban" in 2010, but Islamic dress remains a reliable staple of controversy, from the House of Commons to the Daily Mail ("Tower Hamlets Taliban: Death threats to women who don't wear veils" was one recent headline).

In A Quiet Revolution, Harvard divinity professor Leila Ahmed sets out the background to this remarkable reversal and the fierce debates that surround it. Ahmed, who grew up in Cairo in the 1940s and 50s, was part of a generation of Muslim women for whom going unveiled was a norm that bore little relation to their level of religious commitment. Exploring changing attitudes to women's dress in Egypt, the cradle of both the unveiling movement and the veil's return, throughout the 20th century, she tackles some of the questions so mauled by journalists and politicians. Why did the veil re-emerge among university-educated and professional women? Is it really a symbol of female oppression? Does it signify rejection of the west? Why can it inspire such fear and revulsion?

The most fascinating and incisive sections examine the roots of these questions in the intimate links between the veil and colonialism. To late 19th- and early 20th-century colonial officials, traditional forms of veiling and seclusion were clear evidence of women's "degradation" by Islam, the religion's inferiority to Christianity, and the absolute necessity of western rule over the backward societies that followed it. In his 1908 book Modern Egypt, Lord Cromer, the country's former consul general, contrasted such practices with the freedoms of the west. "The only restraints placed on [a British woman's] movement," he reflected piously, "are those dictated by her own sense of propriety." (At home, meanwhile, in his role as president of the Men's League for Opposing Woman Suffrage, Cromer fulminated against the horrors of "the unsexed woman visiting the polling booth". In Egypt, he put a stop to free state primary education for both sexes and denied funding to the country's only school for women doctors.)

Such anecdotes indicate how little western rhetoric around veiling has moved on. In the wrangles over the French ban, Nicolas Sarkozy described face veils as "a sign of enslavement and debasement", and former immigration minister Éric Besson labelled them a "walking coffin". Now as then, Islamic dress is enlisted to serve political expediency. In the weeks following the coalition invasion of Afghanistan in 2001, Laura Bush gave a radio address on "brutality against women and children by the al-Qaida terrorist network and the regime it supports in Afghanistan"  for which the burqa became a moral shorthand  while Cherie Blair added that the burqa was "one of the crucial barriers [Afghan women] face". The veil is still the subject of an ideological tug of war  as Ahmed puts it, "a sign of irresolvable tension and confrontation between Islam and the west"  and, she could add, within Islam itself.

From the 1920s to 1960s, unveiling was a symbol of Egypt's desire to emulate western scientific, political and economic success  the majority of Egyptians, as Ahmed points out, had accepted the western view of the veil as "uncivilised". A Quiet Revolution provides a clear and compelling summary of the changes that led to its return: the decline of Arab socialism after 1967, the expanding influence of ultra-conservative Saudi Islam and the Muslim Brotherhood, and the failure of pro-western economic policies. By the 1970s, disillusioned students and professionals were turning to an activist Islam  Islamism  that promised social, moral and political renewal. Observing strict dress became one means of displaying egalitarian principles and conveying the wearer's strength and authority. From a symbol of disempowerment, the veil now, for some, became a mark of liberation.

Over the next decades, the veil gathered a range of new meanings: from an expression of personal faith, solidarity with Palestine, Chechnya or Iraq or allegiance to the ummah, to a safeguard against sexual harassment, a fashion statement, a critique of western "sexism", a call for minority rights, an evangelical tool. Ahmed does not romanticise these rationales  she is clear about the growing pressure on women from both Islamist organisations and preachers and from families, peers and the media. But A Quiet Revolution is a timely reminder that the veil today is a symptom less of an alien fanaticism than of a long political and cultural entanglement with the unveiled west.