We all know of various treaties (such as the Geneva conventions) which prohibit the use of certain types of weapons in war, such as chemical or biological ones.
Are there any examples of weapons or martial techniques from earlier periods in history that were seen as dishonorable or forbidden (whether these rules were codified or not)?
Thanks!
The church spent a fair amount of time in the middle ages attempting (unsuccessfully) to legislate some basic rules of war.
One interesting restriction that came up during the Second Lateran Council was a ban on the use of the crossbow. Due to its gruesome efficacy and the violent manner in which it killed, the council forbid 'under pain of excommunication, the employment against Christians and Catholics of that deadly art, so hateful to God'.
In practice, precisely because of its efficacy, the ban was widely ignored. For example, it was argued that because of the wording, the restriction only applied to intra-Christian conflict, and crossbows could thus be used against non-Christian armies, such as during the Crusades, where they saw widespread use.
There's a fair amount of dissenting opinion as to how seriously this restriction was taken by Christian armies operating in Europe. Obviously, crossbows were widely used during the medieval period, but there's quite a bit of evidence to suggest that even if the restriction on crossbow usage was not enforced, it was certainly considered dishonorable. In a complaint to Innocent III, English ambassadors representing Richard I charged the French King Philip of shooting knights with a crossbow. After the Battle of Rochester in 1215, King John arranged the ransom of the captive garrison, except the crossbowmen, who he had executed.
Some reading on the topic:
JA Brundage,Holy War and the Medieval Lawyers Matthew Strickland, War and Chivalry: The Conduct and Perception of War in England and Normandy Robert Bartlett, The Making of Modern Europe (specifically Chapter 3)