The main Isis offensive at the moment is directed at the Syrian Kurdish enclave centred on the town of Kobane where half-a-million people had taken refuge. Of course this detachment from military realities is not possible, but what is military common sense may be politically embarrassing. But in Syria Isis is somehow to be attacked without aiding the Syrian government or groups that the US and Europeans have previously demonised, such as Hezbollah, from Lebanon, which has acted as shock troops for the Syrian government.

In Iraq, the US task is a little easier because at least it is allied to the elected government in Baghdad.

Advances that have taken place have generally been by Shia militiamen under the direction of Iranian Revolutionary Guards officers and Kurdish Peshmerga, though these did not distinguish themselves when Isis attacked Sinjar in August. In Iraq, three months after the fall of Mosul, the Iraqi army still does not seem able to hold its own against Isis as recent fighting around Fallujah demonstrated. In Syria, the most powerful armed group opposing Isis is the Syrian army, followed by Hezbollah and the Syrian Kurds. Of course, in Syria and Iraq there are ground troops capable of taking advantage of the air strikes, but they mostly belong to armies and militias with whom the US is not meant to be co-operating. Air superiority over the fruit groves of Diyala province or the palm trees of northern Hilla is difficult to use effectively. Isis expertise is in guerrilla warfare and it is only recently that it has used columns of vehicles packed with gunmen and heavy infantry weapons. The shock effect of being bombed will be the less because the Syrian air force has long been bombing rebel-held cities and towns. Its fighters avoid large gatherings and mix with the civilian population. Some of the weaknesses of the air war are already apparent since Isis had evacuated its leaders, fighters and heavy equipment from buildings that were targeted. Isis has already faced bombardment by US planes in Iraq since 8 August, but it is still fighting the Iraqi army around Baghdad. Air campaigns not supported by ground forces can damage the other side but they do not win wars on their own.

The US plan to weaken and ultimately destroy Isis has several political and military weaknesses undermining its long-term success.

The Jihadis Return by Patrick Cockburn