The argument of this article is that the proportionality rule in AP–I does express a doctrine that has real roots in western military practice, but it was not traditionally understood as the severe constraint on military operations that the Red Cross propounds. The western States at the Geneva drafting conference did not resist the proportionality rule. In fact, they were active sponsors of that formulation. They understood that rule to be consistent with past practice, including most Allied tactics in the world wars. At the time of the drafting conference, World War II was still within the personal memory of most delegates and even within the professional experience of some delegates. They understood that they were tightening humanitarian constraints in some ways, but did not think they were totally rewriting the law of war.
Proportionality in Perspective: Historical Light on the Law of Armed Conflict,
San Diego Int'l L.J.
Available at: https://digital.sandiego.edu/ilj/vol16/iss2/1