Proportionality is essential in military operations, particularly when there might be civilian casualties. Expected civilian casualties should not be excessive to the expected military advantage. A small military advantage should not be gained at the cost of what ordinary people would consider a large civilian loss of life. Sometimes it may be better to call off an operation.

This question will necessarily involve a consideration of the Rules of Engagement and the way in which it reflects the political will and the type of conflict that is being fought. Proportionality is the key with a consideration of the anticipated military advantage together with an understanding of the political reality that civilian casualties can affect the perceptions of legitimacy of any campaign.

Henry Shue, ‘Civilian Protection and Force Protection’, in David Whetham (ed.), Ethics, Law and Military Operations, (Palgrave Macmillan, Basingstoke, 2011), p141, 144.