Patrick Cockburn: Only winners from brutal repression of Shia majority will be Saudi Arabia

How to explain the ferocity of the Bahraini al-Khalifa royal family's assault on the majority of its own people? Despite an end to martial law, the security forces show no signs of ceasing to beat detainees to the point of death, threaten schoolgirls with rape and force women to drink bottles of urine.

The systematic use of torture in Bahrain has all the demented savagery of the European witch trials in the 16th and 17th centuries. In both cases, interrogators wanted to give substance to imagined conspiracies by extracting forced confessions. In Europe, innocent women were forced to confess to witchcraft, while in Bahrain the aim of the torturers is to get their victims to admit to seeking to overthrow the government. Often they are accused of having treasonous links with Iran, something for which the New York-based Human Rights Watch says there is "zero evidence".

A simpler motive for the across-the-board repression of the Shia, who make up 70 per cent of the Arab population of Bahrain, is that it is a crude assertion of power by the Sunni ruling class backed by Saudi Arabia. The aim is simply to terrorise the Shia into never again demanding civil and political rights as they did during peaceful demonstrations which started on 14 February in emulation of protests in Egypt and Tunisia.

The tragedy of Bahrain is that none of the present toxic developments were necessary even from the egocentric point of view of the al-Khalifas. Of all the uprisings which have taken place during the Arab Spring, Bahrain had the most ingredients for compromise between protesters and the powers-that-be. The demand of the main opposition was not an end to the monarchy, but greater democracy, less discrimination and an end to the policy of naturalising Sunni immigrants in a bid to change the demographic balance against the Shia.

In practical political terms a deal between government and opposition would have required the king to dismiss his prime minister, Khalifa bin Salman al-Khalifa, who has held his job for 40 years and is famous for his vast wealth and extensive ownership of property in Bahrain.

It never happened. Instead the al-Khalifas panicked, probably thinking they would be the next regime to go down after Tunisia and Egypt. The US, despite having its Fifth Fleet based in Bahrain, suddenly appeared to be a shaky supporter. Saudi Arabia and the monarchs of the Gulf wanted what they saw as a Shia uprising crushed.

The government played the sectarian card, portraying the Bahraini Shia as pawns of Iran and frightening the Sunni minority on the island. It bulldozed Shia mosques and prayer houses. Attending the most peaceful pro-democracy rally before the crack down started on 15 March was portrayed as treason and those that had not demonstrated have been forced to confess that they did.

In the short term, the al-Khalifa's strategy has worked and the opposition is cowed, but the price may be permanent hatred of the majority of Bahrainis for the monarchy. The regime may try to change the demographic balance by driving thousands of Shia from the island by intimidation and sacking. Inevitably it will have to rely on Saudi Arabia to an even greater degree than in the past, making the island little more than a Saudi protectorate.