UK has joined a hard, bloody battle against Isis with no coherent plan

The battle against Islamic State will be long and protracted, the defence secretary, Michael Fallon, has said in broadcast interviews. Defeating Isis in Iraq would be difficult enough but destroying it in Syria, the campaign the UK has now joined, was going to be much harder.

There is a plan of sorts – helping both the Iraqi army and the Kurds – for retaking Iraqi territory held by Isis. But nothing remotely coherent by way of a strategy for destroying Isis in Syria. It is optimistically based on air power and a small band of US special forces.

The RAF airstrike against the Omar oilfield, the opening action of the Syrian campaign was hailed by Fallon as a “serious blow”. It certainly will hurt Isis revenue gathering. But the terror group has other sources of revenue and is better financed by far than either al-Qaida or the Taliban.

Isis is also strategically and tactically astute, its military core made up of former officers in the forces of Saddam Hussein. It is not going to be dislodged easily or any time soon from its Raqqa stronghold.

Asked if there was a coherent plan for defeating Isis, Gen Mike Flynn, who retired last year after three years as the head of the US Defence Intelligence Agency, told the Guardian in an interview: “No. No. We don’t [have one] at all. It’s totally incoherent and it’s piecemeal.”

Since the US airstrikes in Syria and Iraq began in September last year, the US administration has been torn between Barack Obama’s unwillingness to be drawn into another Middle East conflict and a need to destroy Isis. The compromise was to stick to airstrikes and avoid as far as possible putting US combat troops on the ground.

That is changing. A new strategy is evolving. Gen John Allen, who had been the US president’s special envoy responsible for operations against Isis in Syria and Iraq until September, outlined that strategy at a Chatham House meeting in London just hours before the Commons vote.

The aim is to squeeze Isis. “We are going to pressure them around their periphery,” he said. So what happens next? US special forces will target the Isis leadership. Roads linking the group’s headquarters in Raqqa to centres such as Mosul in Iraq and elsewhere will be severed. The group’s finances will be targeted, too, such as the revenue raised from oilfields in eastern Syria.