Two decades ago I had tea with one of Ulster’s most infamous murderers in his home. It was a strange occasion. We sat drinking from china cups and eating slices of fruit cake served from a silver stand, while my host, Billy Wright – otherwise known as King Rat – bragged about bloodstained activities on the frontline of the Troubles. As he sat there in his blue denim shirt and jeans, I was struck by the incongruity of this loyalist killer talking so brazenly about the most terrible deeds while serving cake on paper doilies.

Wright crops up briefly in this absorbing attempt to answer a difficult question: does terrorism actually work? King Rat was called “one of the most efficient and ruthless killers” on the loyalist side by a government minister, leaving behind him a trail of up to 20 deaths and many devastated lives. Yet his lethal activities began in response to the IRA slaughter of 10 Protestants in south Armagh. And this shows how terrorism can backfire so disastrously; instead of protecting Catholics, as proclaimed, the IRA violence sparked many more murders.

Perhaps most depressing are the testimonies of those who kill and maim to feel a twisted sense of celebrity or power

The question in this book’s title is complex, controversial and near-impossible to answer given the many varying strands woven into the tapestry of history. But that does not make this attempt by Richard English, a Belfast-born professor of politics at the University of St Andrews, any less interesting. He has spent 30 years studying the subject and, as we know all too well, terrorist outrages grab attention and promote causes with sickening ease. One expert even calls it “performance violence” – although its threat tends to be wildly exaggerated.

The author admits some people might struggle with daring even to ask whether terror works. He carefully sets out his criteria, saying that even if stated goals are not achieved, there can be partial success through secondary strategic aims. Much of the book focuses on four case studies: al-Qaida, the Provisional IRA, Hamas and the Basque separatist group, Eta. In his conclusion, however, he skims through many more from the African National Congress, now governing in South Africa, down to the Free Wales Army who “failed miserably in their small-scale efforts”.

The difficulties of analysis are shown by al-Qaida. Clearly it has not achieved its core objective to force the US and allies from the Muslim world; instead, its actions reinforced Washington’s involvement, often in a violent and destructive manner. Osama bin Laden underestimated the strength of his enemy, influenced by the speed with which the Americans pulled out of Somalia after 18 soldiers were killed there in October 1993. Additionally, for all the publicity given to Islamic State, the regimes in most Muslim countries are not those desired by the jihadis.

The British army in the streets of Derry, Northern Ireland, after the Apprentice Boys’ march during the Troubles. Photograph: Alain Le Garsmeur/Getty Images

Yet as English also points out, al-Qaida violence has hurt the US and its allies, both economically and through loss of life. He concludes that the group embodies a wider truth about terrorism: “the capacity of small numbers of terrorist zealots to change the world, but not entirely as they would have wished or anticipated”. It also shows the paradox of terrorist publicity: atrocities can grab attention, but often backfire on the perpetrator’s cause, as we saw after 9/11 or more recently in France.

Northern Ireland is even tougher to assess, given the length of struggle and extent of influences on the current state of play there. IRA bombs and bullets have not achieved a united, independent Ireland. But did they help bring about a milder form of self-determination, ensuring nationalists the capacity to determine their own affairs? While former Provos are quoted saying they failed dismally and it was all “a futile, useless waste of lives”, those involved in peace negotiations admitted they focused on those using violence, given their aim of stopping the bloodshed.

Ultimately English ducks his own question, insisting there can be no simple answer given the overwhelming complexities involved. Yet that does not make his work less valid. Perhaps most depressing are the testimonies of those who kill, maim and destroy to feel a twisted sense of celebrity or power. One Republican boasts there was no shortage of women “prepared to give more than the time of day” to terrorists. A second talks of “great comradeship”. A third simply says: “I felt important.”

Does Terrorism Work? is published by Oxford University Press (£25). Click here to buy it for £20.50