On 8 January, Mahinda Rajapaksa, who has dominated Sri Lankan politics for a decade, was defeated in the country’s presidential election, thus missing out on a third successive term in office. Incredibly, Rajapaksa’s victorious opponent, Maithripala Sirisena, was a member of his own government only a few months ago. Sirisena’s decision to jump ship and challenge Sri Lanka’s strongman (and his family – three of Rajapaksa’s brothers were also government ministers) unleashed waves of anger and dissatisfaction against Rajapaksa’s government and all its works. A largely unexpected political earthquake is now under way. To understand why, read Samanth Subramanian’s This Divided Island.

But this excellent, powerful book is more than just an account of how the country reached this situation. Looking beyond the confines of Sri Lanka, it also conveys an enduring truth about the nature of all modern conflicts: that how you win a war is just as important as winning it in the first place. Rajapaksa’s popularity with the Sri Lankan electorate rested on his role as the man who finally defeated the Tamil Tiger separatists after a twenty-six-year civil war in a bloody showdown on the beaches of the northeast of the country in early 2009. This, of course, endeared him to Sri Lanka’s Buddhist Sinhalese majority, who make up the core of his support. Yet the Sri Lankan army’s final assault on the largely Hindu Tamils, now well documented in books such as Frances Harrison’s excellent Still Counting the Dead, published in 2012, was so barbaric, callous and merciless that it poisoned the well of Sri Lankan politics and ruptured the country’s relations with the West.

Far from bringing peace to the island paradise, as Sri Lanka’s tourist board would have us believe, the extreme violence deployed against the Tamils has merely engendered more violence, further divisions and more misery. Picking up from where Harrison and others left off, Subramanian, talking in Colombo to the shell-shocked survivors of the civil war several years after it formally ended, writes:

Outright battle had stopped, but an unbroken arc of violence stretched from the war right into our midst. The present conversed with the past. The Rajapaksas presided over the peace in much the same way that they had presided over the war, with arrogance and force. People still lived in fear, and some of them still died in sudden, unnatural ways. Anger still rippled through the island. The state still pummelled its society to submit before its powers. Having acquired the temperament of a country at war, Sri Lanka had forgotten any other way to live.

Thankfully, Subramanian, an Indian journalist from Chennai (formerly Madras), the capital of Tamil Nadu and centre of the worldwide Tamil community, has no truck with the callous, brutal and totalitarian Tigers. He shows, as if we needed reminding, that they became, in the end, just as murderous towards their own people – in the name of their self-declared state of Eelam – as they were towards their Sinhalese oppressors. But the defeat of the Tigers did not mean an end to conflict. In some of his best chapters, Subramanian shows how the sectarian violence visited by the Sinhalese majority upon the Tamils has now been refocused against another minority, the country’s Muslims, who make up just under 10 per cent of the population. The rhetoric deployed against Muslims is often just as incendiary and provocative as anything that was ever said against the Hindu Tamils and has led, during the last few years, to attacks on mosques and Muslim shops and homes.

Much of this has been organised by the sangha, the country’s Buddhists monks, tacitly backed by Rajapaksa’s government in order to bolster its standing with Sinhalese nationalists. Far from being the peace-loving spiritualists of popular imagination, right-wing nationalist monks have founded organisations such as the Bodu Bala Sena (the ‘Army of Buddhist Power’, more or less) to attack the Muslim minority. Organisations like this have flourished in the atmosphere of fear and intimidation that is a direct consequence of the war years; critics of Rajapaksa’s government regularly disappeared and journalists were continually harassed.

Subramanian tells this sorry story with verve and compassion, relentlessly tracking down survivors of, and witnesses to, Sri Lanka’s agonies, both on the island itself and abroad too – in Canada, Britain and elsewhere. Very importantly, he puts the civil war into its historical context. He shows, most adroitly, how the Tamils had perfectly legitimate grievances against the Sinhalese-dominated governments that began to marginalise them in the post-independence years, but he also demonstrates how the Tigers comprehensively undermined their own cause through their brutality. ‘This was the war the Tigers lost first, the war for the unconditional affections of the island’s Tamils and for the uncontested right to fight on their behalf.’

Hopefully, this election will prove to have been a turning point, the moment when a majority of Sri Lankans, of whatever faith and ethnicity, turned against the malevolent thuggery and authoritarianism of recent decades. As Samanth Subramanian shows all too well, if Sri Lanka is ever to end its divisions the country badly needs some real truth and reconciliation rather than sectarian triumphalism masquerading as peace.