Britain has joined a war against Islamic State (Isis) within a political framework that guarantees frustration if not failure. The House of Commons was rightly wary of another open-ended foreign intervention in Iraq, Syria or anywhere else. But, while MPs are conscious that Britain is entering a minefield, they were much less good at identifying where the mines are and what, if anything, can be done about them. As in 2003, the US and Britain are plugging themselves into a series of inter-related conflicts in Iraq and Syria in which the main players have very different agendas from what they pretend.

Take the current Isis offensive against the Kurdish enclave of Kobane in northern Syria on the border with Turkey, where 300,000 Kurds are squeezed into a smaller and smaller enclave as they battle better armed Isis fighters. Some 200,000 Syrian Kurds have already fled across the Turkish border. Here, if anywhere, the US could have deployed its airpower to attack the advancing militants. It was US air strikes that helped to save the Iraqi Kurdish capital Erbil in August so why not do the same for Kobane?

Strangely, until yesterday the US was using its airpower everywhere in Syria except Kobane where Isis has launched its most serious offensive since US air attacks on Syria began. It has seized 64 villages, using tanks and artillery barrages from guns captured from the Iraqi and Syrian armies. Why the American reticence? It appears to be motivated by a wish not to offend Turkey which never cared for the semi-independent Kurdish cantons, home to many of Syria’s 2.5 million-strong Kurdish minority, that have grown up across its southern border since 2011.

Its actions are strong evidence that Ankara can see the advantages of using Isis against the Kurds. Reporters on the ground on the Turkish side of the border say that Isis militants still found it easy last week to cross backwards and forwards, unlike Turkish Kurds wanting to fight Isis. An observer in Turkey asks the question: “Why Isis fighters are still being taken across the border into Turkey to be treated in hospital for their combat wounds, when medical staff treating non-violent but injured protesters in Gezi Square are put on trial for ‘assisting terrorism’?”

For all Turkish President Recep Tayyip Erdogan’s statements at the UN in New York that he opposes Isis, the militants receive a degree of toleration from the Turkish state. This was graphically illustrated by pictures on successive days last week of police treatment of two demonstrations in Istiklal Caddesi in the heart of Istanbul. The first shows pro-Isis demonstrators holding a long white banner untroubled by the police. The second picture shows a group in the same street the following day protesting at the imposition of religious education who are being beaten by police in full riot gear.

It is not that the Turkish government is hand in glove with Isis, but that getting rid of President Bashar al-Assad as well as weakening the Syrian Kurds has been higher up Mr Erdogan’s agenda. By going along with this, the US is committing the same mistake it made in Afghanistan after 2001 when it failed to respond to Pakistan’s covert but crucial backing for the Taliban. Several US diplomats later saw this as a massive error that doomed from the start American and British intervention in Afghanistan.

The point to keep in mind here, as Britain makes its first largely symbolic military intervention in Iraq, is that there are limits to what can be achieved by military means in this crisis. This is being obscured by the bombast accompanying the first days of military action with military experts pontificating about the terrible damage being done to those targeted and television viewers ghoulishly watching pictures of missiles and bombs destroying supposed Isis command and control centres.

But Isis is a guerrilla army with long experience of being bombed by the American, Iraqi and Syrian air forces. It is worth recalling that the US had 150,000 soldiers in Iraq and an air armada overhead at the height of its intervention in Iraq in 2007 and still failed to eliminate al-Qaeda in Iraq and other Sunni resistance groups. There is no reason it should be any different this time round.

There is a role in Iraq and Syria for foreign airpower to act as a fire brigade to stop Isis from storming Erbil in August or taking Kobane now. But go beyond this limited but important role and air strikes swiftly become counter-effective. It all depends in whose interests in these multi-faceted civil wars that airpower is being employed. It is here that political ignorance or self-deception becomes so dangerous, such as that of British Defence Secretary Michael Fallon declaring that we would be using British air strikes in support of Iraq’s newly formed inclusive and representative government under Prime Minister Haider al-Abadi. This administration is apparently acceptable to Iraqi Sunni, unlike that of the violently sectarian Shia-dominated government of Prime Minister Nouri al-Maliki.

The impression given by Mr Fallon is that if American, British or French air strikes help to clear the way for the Kurdish peshmerga or the Iraqi army, then they will be greeted with open arms by the Sunni of Mosul. Except that none of this is true. The new Iraqi government is much like the old and equally, if less overtly, sectarian. The most effective fighting force of the Baghdad government is the Iranian-managed Shia militias of which the Sunni are terrified and with some reason.

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I had experience of this in 2003 when Kurdish peshmerga captured overwhelmingly Sunni Mosul after advancing under an American air umbrella. The Iraqi army was breaking up so there was no resistance in Mosul until the Kurds moved in. At first there was jubilation that Saddam Hussein had fallen, but this was rapidly replaced by fear and anger that the Kurds were in charge. Shooting began as loudspeakers called for vigilantes to build barricades and stop the Kurds. I had driven from Erbil with a Kurdish driver called Yusuf who was almost lynched when a crowd leaving a Sunni mosque noticed that our vehicle had licence plates from a Kurdish province. I had walked into medieval Christian quarter but when I got back I found that Yusuf was looking shaken and said that he had almost been killed by a hostile crowd in which one man kept shouting: “Let’s kill him and burn the car.”

What Britain should be doing in addition to sending the Tornadoes is to do everything possible to get negotiations going between the main outside players in the Iraq-Syria crisis. These would include the US, Russia, Saudi Arabia and Iran as well as inside players such as the Syrian government, Syrian Kurds and non-Isis opposition to Assad. The only way to eliminate Isis long term is to look for a way of de-escalating the crisis so that local parties do not all feel that they are fighting for their lives. Isis is essentially a war machine, and so long as the Syrian war goes on it cannot be beaten.