“Advocates argue that the rule-based approach has one major virtue: it is always clear why the machine makes the choice that it does, because its designers set the rules. That is a crucial concern for the US military, for which autonomous systems are a key strategic goal. Whether machines assist soldiers or carry out potentially lethal missions, ‘the last thing you want is to send an autonomous robot on a military mission and have it work out what ethical rules it should follow in the middle of things’.”