<p>governing the actual conduct of armed conflict (jus in bello) and not to the rules governing the resort to armed conflict (just ad bellum). For most purposes, jus ad bellum is a separate question meriting separate attention.
There are a variety of internationally recognized legal bases for use of force in relations between States, found in both customary and conventional law. Generally speaking, however, modern jus and bellum (the law of resort to war) is generally reflected in the United Nations Charter
The major difficulty in the conduct of foreign policy in wartime was that it was completely dependent upon factors over which the Foreign Secretary had no control