The 2016-17 Iraqi offensive that recaptured the city of Mosul from the Islamic State have demonstrated the inability of contemporary armed forces to retake urban areas from a determined and ruthless enemy without either suffering debilitating casualties or causing thousands of civilian deaths and virtually destroying the city itself. The enemy’s willingness to refuse civilian evacuation via a humanitarian corridor and effectively take the inhabitants hostage is all it takes to impose this tragic dilemma on an attacking force. The civilian death toll of the battle of Mosul alone is estimated to have reached between seven and forty thousand, with almost one million people internally displaced and large portions of the city levelled. Avoiding another such tragedy should be a priority for all practitioners and theorists of urban warfare. Indeed, confronting and defeating this challenge may be the most important task for ethics, theory and practice of urban combat in the coming decade.
I argue that the only viable way of escaping the hostage siege dilemma consists of incorporating large numbers of unmanned and autonomous weapon systems into the blue force structure and using these to substitute for artillery and aerial fires presently being used to overpower defenders. While other measures may be used to marginally improve the outcome of hostage city assaults, only the automatization of the assault can dramatically change the calculus and in result either discourage rogue actors from creating hostage city dilemmas or defeat them decisively while suffering unequivocally proportional casualties.
I proceed as follows: first, I provide an account of the 2016-17 Coalition assault on Mosul, giving special attention to the events and features relevant to the hostage city dilemma. I then use this case study to introduce the theoretical concept of the hostile city and the ethical dilemma it creates, discussing possible objections and making the case that the circumstances of the Battle of Mosul are bound to repeatedly transpire in the future. This generates a duty to find a way out of the hostage city dilemma. I argue that widespread use of unmanned and autonomous weapon platforms constitutes a viable way of assaulting hostage cities in a manner that assures respect for the ius in bello principles, proposing several ways in which such weapons may be designed and used to drastically limit both military and civilian casualties. Concluding that it may be not only permissible but morally required to employ autonomous weapons in the hostage city scenario, I briefly discuss the implications of this conclusion for a wider debate concerning the moral feasibility of autonomous weapons.