The early days of April 1865 found the New York Irish American rejoicing at the imminent prospect of the Civil War's successful conclusion. The killing and dying had not yet ceased, but they were already eagerly anticipating the ‘next war’, and a long-hoped for ‘dash at John Bull’. ‘Let America but say the word,’ the newspaper declared, ‘and the ‘Union Jack’, the red flag of oppression and spoilation, goes down — at once and forever — before the banner of Freedom.’ Before 1865 was out, handfuls of Civil War veterans were already arriving in Ireland, hoping to make that conflict a reality. Like all the martial plans put into operation by the Fenians then and in the years that followed — in Ireland, Britain and Canada — their efforts ultimately failed. But seeking victory through direct military action was not the only card the Fenians had to play. The tense and often fractious relationship between Britain and the United States presented them with an opportunity to exploit existing divisions, and perhaps even bring about the clash the Irish American so craved. Lucy E. Salyer's study, which runs to twelve chapters arranged in three distinct sections, focuses on the Fenians’ central role in reigniting a long-running dispute between the two nations — one that revolved around citizenship.

While the British insisted on the perpetual and unalterable allegiance of her subjects, the Americans held that an immigrant should have a right of expatriation and be able to choose (and change) their allegiance. It was an argument that had already contributed towards war once before, in 1812, and remained unresolved. Enter the Fenians. The cause célèbre that propelled this issue into focus had its origins in what was on its face a disastrous attempt by American members of the brotherhood to provide arms and expertise for insurrection in Ireland. The expedition had set out from New York in April 1867 aboard the Jacmel — soon to be rechristened the Erin's Hope — her hold stuffed with 5,000 arms, three pieces of artillery, 1.5 million rounds and more than forty Fenians.

The arms never made it ashore but most of the men did. The majority landed at Helvick Head, County Waterford, only to be detained and arrested in short order. Among their leaders were John Warren and Augustine Costello, both Irish-born naturalised American citizens, and William Nagle, a birthright American citizen due to his New York nativity. During their incarceration and subsequent prosecution under the Treason Felony Act, these men's citizenship status quickly came to the fore. Their efforts to keep it there were typified by John Warren, who dramatically dismissed his attorneys in order to place his case ‘in the hands of the United States government’, in essence claiming he was not just defending himself, but also his country of adoption. After many long months in confinement — and in Warren and Costello's case the handing down of a lengthy custodial sentence — all three men were ultimately released to return to America. Their efforts failed to bring on the ‘next war’, but the furore they created was instrumental in generating momentum towards the passage of the U.S. Expatriation Act of 1868 and the Naturalisation Treaty between Britain and the United States in 1870, which formalised the right of expatriation for British subjects and U.S. citizens.

Under the starry flag is a well-constructed and highly readable book. Salyer provides a compelling account of the Erin's Hope, but the volume's major contribution comes not in what it reveals about the Fenians, but in how it places that crisis within the wider context of the international citizenship debate. It builds on the work of scholars such as Christian Samito in employing the Irish American experience as a vehicle to examine wider questions surrounding the changing nature of citizenship in the nineteenth-century United States. In doing so, the author deftly interweaves the story of her central characters — John Warren and William Nagle — with the actions and reactions of major players in America, Britain and Europe, an ensemble cast that includes Charles Francis Adams, the weary and often exasperated American ambassador to Britain, and William H. Seward, the increasingly legacy-conscious U.S. secretary of state. Salyer's welcome analysis of contemporary American expatriation negotiations with the North German Confederation and China and her examination of the role played by race and gender in defining and limiting access to citizenship are particularly useful in considering the Irish American experience in comparative perspective. All told, this is a very fine book. It will prove essential reading across a broad range of historical fields, not least for scholars interested in the Fenians, Irish America and the part the Irish played in the story of American citizenship.