Chapter 4 explains the relevant rules of armed conflict that provide for the protection against the effects of hostilities. To the extent that humanitarian law protects civilians and civilian objects, it also protects foreign investors and their investments, as far as natural persons and tangible assets are concerned. The chapter shows how the law of armed conflict balances military and humanitarian concerns and illuminates the operation of the principles of distinction, proportionality, and precaution. In analysing the limitations of this protection, the chapter further identifies circumstances in which harm to foreign investors and their investments may be lawful under international humanitarian law. In particular, the chapter shows how foreign investments can easily become military targets and under which circumstances inflicted damage can be an acceptable side effect of military operations. The chapter thus forms the basis for the subsequent examination of international humanitarian law’s impact on individual investment treaty standards.