Anyone watching the Commons debate in the first week of December on bombing Syria could easily have been misled by the hype. An impression was left that somehow RAF Tornados and British Brimstone missiles were going to have a decisive impact in the fight against Islamic State (Isis).

The reality is, as David Cameron will discover on Monday morning, on his first day back after the holidays, Isis is not going to disappear anytime soon. The talk at Westminster and elsewhere around the country will be of flooding, rail fares and impending welfare cuts – but also the emergence of what looks like a replacement for Mohammed Emwazi, the British propagandist for Isis who was dubbed Jihadi John.

There was more than an element of triumphalism in November when the US and UK announced that Emwazi had been killed in a drone attack in Raqqa, the organisation’s stronghold in Syria. That triumphalism, though understandable, was misplaced.

He was linked to horrific beheadings but he was never a senior member of Isis, whose leadership is made up of hardened fighters, ex-members of Saddam Hussein’s Iraqi army or al-Qaida in Iraq. His only advantage was that he had an English accent.

Mohammed Emwazi was never a senior member of Isis. Photograph: Uncredited/AP

Any hope that the sophisticated Isis propaganda machine, which is effective in recruiting foreign fighters and spreading fear, was going to be seriously damaged by the killing of Emwazi has proved to be equally misplaced. With at least 300 known Britons active in Syria and Iraq, mainly with Isis, it was not going to be hard for the organisation to find another English speaker to take his place.

So the search by the UK and US intelligence services begins again to find and kill another relatively low-ranking Isis figure. It is understandable but is a distraction from the main fight.

Isis poses a threat not only to the Middle East but Europe and other parts of the world. What Cameron is guilty of is failing to be honest about the limitations of the response of the US, UK, France, Germany and others so far.

It is irresponsible to exaggerate the military action being taken in response. Isis is not going to be defeated by extending RAF bombing to Syria or sending in an extra SAS unit, or a drone strike on a low-ranking foreign recruit fluent in English.

US and UK counter-terrorist and military specialists repeatedly make two key points when asked about the current situation in Syria. One is that Isis can only be beaten by land forces that the US, the UK, France and other countries, including Russia, are not yet willing to do. In Iraq, there is the Iraqi army and the Kurdish peshmerga that the US-coalition can support. But in Syria there are no such local partners. Nor is there any sign yet of one or more of the countries in the region providing such an army.

Secondly, counter-terrorism and military specialists are nearly unanimous in arguing that Isis cannot be beaten by military means alone. Al-Qaida in Iraq was defeated militarily but it was in turn replaced by Isis.

The ideas of militant Islam have to be vigorously countered with an alternative message and by the establishment of a viable political system in both Iraq and Syria, with maybe a redrawing of borders. None of these things are close to happening.

The big breakthrough for Isis was when it took Mosul in northern Iraq in June 2014. The western media registered this at the time but few realised the significance. Today, Isis – or groups claiming allegiance to it – is active in 11 countries in the Middle East, Africa and Asia. In Iraq, in spite of losing much of Ramadi over the last few weeks, it still controls Fallujah and Mosul, and has lost little territory in Syria. And it has spread even more fear throughout Europe.

Since the Commons vote to extend bombing to Syria, the RAF has flown relatively few missions to Syria, mainly because of a shortage of targets. Instead, it has continued to do mainly what it was doing before, conducting raids in support of the Iraqi army and the peshmerga.

The US and UK involvement in Iraq and Syria – with the possibility of hundreds of UK troops being sent to Libya also – amount to little more than pinpricks. At best, all they are doing is containment. There is no sign of an end anywhere in sight in the battle to defeat Isis, which as it latest recruit demonstrates, looks set to last a generation.