After major losses in Iraq and Syria, London terror attack is an attempt by Isis to prove it’s still a major force

The indiscriminate slaughter of ordinary members of the public on London Bridge and in Borough Market on Saturday night is fully in keeping with the operational methods of Isis. They have yet to claim responsibility, but it is extremely likely that they were ultimately behind an attack that bears so many Isis hallmarks.

The killings were probably triggered by a pre-arranged instruction to a cell or individual in Britain, the order coming from within the Isis apparatus, and not in response to a more generalised call to its sympathisers to make attacks in Europe and elsewhere. Isis is more professionally organised than is generally supposed, going by its track record over the last five years; its military and terrorist tactics traditionally involve those in charge deciding overall objectives and timings, but leaving local operatives to determine everything else.

Mass murder by Isis of defenceless civilians is frequently carried out in well-known or iconic places to ensure maximum publicity and to spread as much fear as possible. The perpetrators, for the most part, die along with their victims or soon afterwards, making a deliberate public demonstration of their religious commitment. The latest killings in London have all these characteristics, and are very similar in this respect to previous atrocities on Westminster Bridge carried out by Khalid Masood, and in the Manchester Arena by Salman Abedi.

The timing of these three acts of terrorism is most likely connected to Isis setbacks and retreats on the battlefield in Iraq, Syria and Libya. Its fighters have lost most of Mosul – the centre of the self-declared Caliphate since Isis captured the city in 2014 – which Iraqi security forces have been assaulting for seven months. The US-backed Syrian Kurds and their Arab allies have said in the last few days that they are about to storm Raqqa, the isolated Isis de facto Syrian capital on the Euphrates River.

Isis uses terrorism in a deliberately sadistic and attention-grabbing way to counter-balance any perception that it is weakening or is fought out. In return for minimum expenditure of men and resources on its part, it can demonstrate to the world that it is still in business despite its loss of territory. It welcomes denunciations because its savagery is geared to topping the news agenda. For this purpose, Isis films its own massacres, ritually decapitates journalists, burns captives alive or drowns them in cages. Last week, a bomb exploded outside an ice cream shop thronged with children in Baghdad killing at least 15, with some reports saying 30 people were killed and dozens more injured.

It has been suggested that the Western mass media plays into the hands of Isis or al-Qaeda by the wall-to-wall coverage of their crimes. But self-censorship is unrealistic since there is overwhelming and understandable public demand for information about terrorists and terrorism which needs to be satisfied. Where authoritarian governments censor or play down Isis and al-Qaeda acts and capabilities, as they do in much of the Middle East, the result is simply to create a vacuum of news and to discredit any media outlet that is silent.

The terrorist tactics used by the three men shot dead in Borough Market in the midst of their killing spree, have been developed by Salafi-jihadi movements over the last 20 years. The most notorious example of a suicidal terrorist attack of this nature was 9/11, when the World Trade Centre was destroyed, but they were used on a mass scale from beginning of the war in Iraq in 2003, though they were not pervasive in Afghanistan until later.

The effectiveness of this sort of terrorism is that the entire population is the target and cannot all be defended. Fanaticism but no great amount of military expertise is necessary, so Isis is not depleting its limited number of experienced fighters. Many of the untrained Isis supporters who arrived in Syria and Iraq in recent years, who did not speak Arabic and had no other useful skills, were deployed as suicide bombers, with more than 600 being dispatched, often in vehicles packed with explosives, in the first weeks of the Iraqi security forces’ advance into Mosul last year.

A further aim of the suicide bombings in Iraq and Syria is to spread out the security forces and to discredit the government in the eyes of its own people, on the grounds that it cannot defend them. In these countries, the ability of bombers to pass through numerous checkpoints without being stopped is often blamed on corruption, but, even when they are stopped, they can cause heavy casualties by blowing themselves up at a crowded security post.

The emphasis in Britain on seeking to stop Isis attacks by monitoring and neutralising some 23,000 Salafi-jihadi suspects can never be more than partially successful. Only five people are known to have been directly involved in the Westminster, Manchester and London Bridge killings, and these may have been selected, or self-selected, because they were not on a list of prime suspects. But the real key to preventing terrorist attacks lies not in Britain at all, but in eliminating Isis sanctuaries in Iraq and Syria which remain the inspiration and guiding hand for Isis worldwide.