Warning UK air strikes against Islamic State may need to go on for years

Britain may need to carry on air strikes against IS for years to come, even if there is little prospect of delivering a knockout blow, warned a military think tank.

A report by the Royal United Services Institute said that without a wider political settlement in Syria, the UK could have to sustain its military campaign against the extremists “over a period of several years”.

Even then, the report said, it is possible, “perhaps even likely”, the operation will end without having achieved a “decisive strategic effect”.