The children (and wives) of foreign ISIS fighters 71 treatment of detainees and the possibility for States of nationality to resort to diplomatic protection, are relevant also to FTFs.8 Ever since foreigners started to flock to the Middle East to join the parties involved in the armed conflicts fought in the region, there has been a widespread confusion concerning the use of the terms foreign fighters (FFs) and FTFs. FFs have been defined as ‘individuals, driven mainly by ideology, religion and/or kinship, who leave their country of origin or their country of habitual residence to join a party engaged in an armed conflict’,9 thus placing the accent on the individuals’ departure from their State of origin in order to support one of the actors, an armed group or a State’s armed forces, engaged in an armed conflict. The term FTFs, instead, refers to ‘individuals who travel to a State other than their States of residence or nationality for the purpose of the perpetration, planning, or preparation of, or participation in, terrorist acts or the providing or receiving of terrorist training, including in connection with armed conflict.’10 This definition, enshrined in a widely commented upon UN Security Council Resolution, calls on Member States to deal specifically with those who travel abroad with a ‘terrorist intent’ as opposed to those who travel abroad only to ‘fight’.11 Moreover, Resolution 2178 8 One of the most striking features of the so-called Caliphate − spanning over parts of both Syria and Iraq since its establishment in 2014 − was the ability of ISIS to lure a large number of foreigners. According to the most cited data, in a very short amount of time 41,490 international citizens from more than 80 countries became affiliated with ISIS. Some 5,000 men, women and children travelled from Europe to Syria and Iraq since 2012. An estimated 1,500 individuals have returned to Europe so far, whereas precise information is not always available with regard to those who were born in Syria or Iraq, died, fled elsewhere, have been captured and are currently detained. See J Cook and G Vale, ‘From Daesh to “Diaspora”: Tracing the Women and Minors of Islamic State’ ICSR (2018) 7 <https://icsr.info/wp-content/uploads/2018/07/ICSR-Report-From-Daesh-to‘Diaspora’-Tracing-the-Women-and-Minors-of-Islamic-State.pdf>; T Renard and R Coolsaet (eds), Returnees: Who are They, Why Are They (Not) Coming back and how Should We Deal with Them? Assessing Policies on Returning Foreign Terrorist Fighters in Belgium, Germany and the Netherlands (Egmont Paper 2018) 3. 9 A de Guttry, F Capone, C Paulussen, ‘Introduction’, in A de Guttry, F Capone, C Paulussen (eds), Foreign Fighters under International Law and Beyond (Springer/Asser Press 2016) 2. For a detailed overview of the history of the FFs phenomenon and the challenges ahead see D Byman, Road Warriors. Foreign Fighters in the Armies of Jihad (OUP 2019). 10 UN Doc S/RES/2178 (2014) (24 September 2014) preamble. 11 K Ambos, ‘Our Terrorists, your Terrorists? The United Nations Security Council Urges States to Combat “foreign terrorist fighters”, but Does not Define “Terrorism”’ EJIL:Talk! (2 October 2014) <www.ejiltalk.org/our-terrorists-your-terrorists-the-united-