I was looking for ANYTHING that could be used to show some degree of acceptance of such restrictions. An imperial letter of instructions, a military code, a standrd text in "orders of the day" ..... really anything. Either for Russian or French.
Absent such, what exactly was the illiterate, unschooled, quickly trained conscript supposed to have access to that would have enabled him to know of the principles of Vattel and Martens (or similar) ?
And, if these governments did not agree with the principles of Vattel and Martens, who are we to retroactively decide for them that they should have accepted such principles ?
If an American or Russian pilot goes on vacation to Canada, do you arrest him and try him for war-crimes if has been dropping cluster bombs during his last deployment ?