Janina Dill is a Lecturer at the Department of Politics and International Relations at the University of Oxford.] In the ongoing military campaign ‘Protective Edge’ the Israeli Defence Forces (IDF) consistently issues warnings before air strikes against targets in Gaza. The population is warned of impending attacks with phone calls, text messages or so called ‘knocks on the roof’ (dropping of non- or low-impact explosives on the intended target). The warnings play a central role in Israel’s claim that, contrary to Palestinian armed groups, namely Hamas; it obeys the strictures of international law. ‘While the IDF goes to extraordinary lengths to avoid civilian casualties, Hamas deliberately puts civilians in the line of fire, the IDF maintains on its official blog. The First Additional Protocol to the Geneva Conventions, the relevant sections of which have the status of customary international law, in Article 57(2) c indeed prescribes that ‘effective advance warning shall be given of attacks which may affect the civilian population, unless circumstances do not permit’. Warnings, their frequency and form, are at the centre of a narrative that Israel does not simply comply with, but goes beyond the call of international law in its care for the civilians of Gaza. ‘Israel's use in the Gaza Strip of non-lethal warning shots to the roofs of buildings which constitute military targets … is not legally obligated’, the Military Advocate General’s Corps holds. Media commentary commends Israel for giving civilians a way out without even being obliged to do so. This is a misunderstanding of Article 57. The provision establishes an unequivocal obligation to warn before attacks that implicate the civilian population – as air strikes against a territory as densely populated as Gaza will regularly do. Granted, it is not an absolute obligation. The law recognizes that sometimes it may not be possible to warn. Crucially the provision does not say ‘warn if possible’, but ‘warn unless impossible’. It is open to interpretation when that is the case and reasonable people may disagree, but the default is to issue a warning and it is a failure to do so that requires explanation. Warnings are not acts of charity. But are the kinds of warnings issued as part of Operation Protective Edge manifestations of the IDF’s commitment to the laws of war? The practice raises two distinct concerns. The first is that the air strikes the IDF carries out after issuing warnings are indicative of a misunderstanding of the legal implications warning before an attack. It has none! The second is the concern that the practice itself violates international law. I discuss them in turn.