Future wars will be more Stalingrad than Star Wars, a US General has said as he warns against a relentless focus on technology.

General Stephen Townsend, the head of the US Army’s Training and Doctrine Command, told British military leaders at the annual Kermit Roosevelt lecture in London, that combat in an increasingly urbanised world will result in a “scale of devastation beyond our comprehension”.

“The future operational environment will be more lethal and on a scale not seen in decades,” he said, as he warned military chiefs that advanced weapons will be of little use in built up areas devastated by fighting.

The Kermit Roosevelt lecture series is an annual exchange of speakers from the UK and US militaries. The initiative for the exchanges originated with Mrs Kermit Roosevelt, whose husband – the son of President Theodore Roosevelt – served in both the British Army and US Army across the two World Wars. Kermit Roosevelt died while on active duty in 1943.

Modern armies have no idea how to fight in these “hyper populated [and] literally unboundable” areas, Gen Townsend told the audience at the Royal United Services Institute. In the battle to liberate Mosul from Islamic State of Iraq and the Levant (Isil), he had had to ask coalition partners if any army still used flamethrowers, as 'bunker buster' bombs had proved useless against fighters dug in amongst destroyed buildings.