In the period between March and June 1999, the North Atlantic Treaty Organisation (NATO) waged a bombing campaign against the Federal Republic of Yugoslavia (FRY). The war began with the suppression of air defence systems followed by attacks against police, military, and paramilitary forces in Kosovo and southern Serbia responsible for the ethnic cleansing of Kosovar Albanians. When this failed to bring Slobodan Milosevic to the bargaining table, NATO escalated the air campaign to strategic targets inside Yugoslavia, including the targeting of dual-use civilian infrastructure. This aroused considerable opposition from human rights NGOs, and sections of public opinion in NATO countries, especially Germany, Italy, and Greece. The Alliance was accused of placing civilians at unnecessary risk, and of violating that body of international humanitarian law pertaining to the protection of non-combatants in armed conflict (hereafter IHL or the laws of war). The Yugoslav government claimed that the bombing killed 2,000 civilians, but most commentators accept the conclusion of a detailed investigation by Human Rights Watch (HRW) that put the figure nearer 500.

NATO's compliance with the laws of war represents an important case for exploring how far law influences the conduct of military operations. Recent studies by theorists in the disciplines of international relations and international law have identified a significant role for legal rules in inhibiting the exercise of power. However, this research has stopped short of examining military security issues, especially in relation to the use of force.