Complicity is a subject that lends itself to an appreciation of assistance and encouragement. This book, which grew out of the doctoral thesis I defended at the University of Oxford in November 2013, depended on a great deal of both. First and foremost, I would like to thank Professor Dapo Akande for his direction and advice on the thesis, both of which were indispensable, and for his warm support and friendship beyond it. I owe him a great deal. I owe an intellectual debt to those who taught me international law, in particular Professor Stefan Talmon, for his rigour and inspiration many years ago, and Professors Ryan Goodman and William Alford. In addition, I am immensely grateful, both personally and professionally, to Professor Liora Lazarus. I am also thankful to my examiners, Professors Andrew Ashworth and André Nollkaemper, and all at the University of Oxford and elsewhere who discussed drafts, chapters, and ideas with me: Sir Frank Berman, Professor Michael Bohlander, Professor Sandra Fredman, Professor John Gardner, Professor Guy Goodwin-Gill, Professor Imogen Goold, Professor Doug Husak, Professor Nina J?rgensen, Dr Maris K?pcke Tinturé, Professor Vaughan Lowe, Professor Catherine Redgwell, Professor Antonios Tzanakopoulos, and Professor Stefan Vogenauer. I would like to thank Farid Ahmadov, Nick Friedman, Ryan Goss, Claire Hewer, Sotirios-Ioannis Lekkas, Thomas Liefl?nder, Kubo Ma??k, Travers McLeod, Dhvani Mehta, Rob Mullins, Brid Ni Ghr?inne, Nikki Palmer, and Laith Tapper for their friendship, help, and advice along the way. I am also immensely grateful to Anna Begemann, Caitlin Goss, and Natasha Simonsen, all of whom read the entire draft and for whose comments it is vastly better. I am thankful to Oxford University Press and its Delegates, and personally to Emma Endean, Merel Alstein, and John Louth for their support and work in turning the draft into a book. In addition, I appreciate all of the work that Dhanuj Nair of Newgen put into shepherding the project to completion and Cheryl Prophett’s excellent copy-editing.