This chapter deals with the core period of extensive inter-communal violence in the Republic of Cyprus, from December 1963 to September 1964. It introduces the arrival of an ICRC delegation and of the UN Peacekeeping Force in Cyprus (UNFICYP), and it elaborates on the actions and the organisation of the paramilitary groups involved, the National Guard and the Turkish Airforce. It sets the facts in a coherent chronological order, accompanied by legal commentary, making extensive reference to previously unpublished archival material. It also provides an extensive study of the Ibrahim case, the case which invoked the application of the Doctrine of Necessity in the Cypriot constitutional order.