States must disseminate international humanitarian law (IHL) and integrate it into military instruction. Implementation of the IHL training obligation was delayed in the UK; when the government asserted that IHL was inapplicable to colonial warfare, resisted the development of the IHL of non-international armed conflict, and was keen to maintain the nuclear deterrent. Absent or perfunctory IHL training correlated with recurrent violations of the prohibitions of torture and inhuman treatment, from the 1950s to the 2000s. Despite official assertions that the British Army’s training in IHL was being reformed following the death of Baha Mousa in British military custody in 2003, there were gradual changes from 2004 to 2011, and more thorough improvements from 2012 to 2017. Training materials for soldiers and officers now offer breadth and detail on IHL, with elements of international human rights law. They implement the 71 recommendations in the Baha Mousa Public Inquiry Report which the Ministry of Defence accepted, and are supplemented by practical training. Yet these are reactive reforms, which still lack norm-by-norm evaluation of soldiers’ understanding. Prohibitions on humiliating or degrading treatment of a sexual nature, and on the intentional infliction of severe mental pain and suffering are (respectively) under-emphasised and absent. References to the necessity of restraint positions (as opposed to the prohibited stress positions) may cause confusion. There is a simplistic suggestion that reprisals are lawful if they are politically authorised. Training reforms have been cited as one reason to close criminal investigations into alleged war crimes: a response which neglects coexistent investigatory obligations.