I was looking through my grandfather's WWII stuff the other day and was caught by the small case of German 9mm ammunition. It looked like regular 9mm but fittingly painted in a sinister black.
I wondered though, why the heck didn't they just use hollow point ammunition? I mean they were going around invading countries and WWII was a war of war crimes. Wouldn't it have made their weapons more deadly to have used hollow point or dum dum rounds?
On a broader note why are hollow points against the rules of war? Gas seems particularly horrible but hollow point seems like a matter of degree. It feels like banning rifles with a certain accuracy. Yes it helps your side, but it also hurts it.
Germany abided the laws of war for the most part. There was a big difference between the Western and the Eastern front obviously.
Like you pointed out this ammunition was banned since the Hague Convention and using this ammuntion would just make the enemy do the same and the advantages would negate each other and it would just result in more suffering.
Nobody follows the laws of war because its the moral thing do to you just do it so your enemy does the same. For a country to break these rules there have to be some conditions. The advantages gained should outweight the disadvantages and you should be powerful enough that it doesn't matter what the rest of the signatories thinks.
During the Battle of the Bulge the Wehrmacht was using vehicles and soldiers without them being properly marked as Wehrmacht going so far to repaint/rework Panthers as M10s. Why would they do that when it is against the laws? Because they were desperate and the Western Allies reaction would be irrelevant. What are they gonna do? Do the same? Doesn't matter they are winning anyways.
On a broader note why are hollow points against the rules of war?
The point of these rules is to minimize the suffering. Dum dum used by both sides would hardly change anything besides more suffering. The casualty ratios would be the same the victor would be the same. There is literally no point that these bullets should be used in war.
Like pointed out before nobody follows these rules out of kindness. Correct treatment of POWs et cetera benefits everybody ( for the most part ). If you obviously plan to exterminate your enemy then these rules are forgotten really fast as we have seen on the Eastern Front where the Wehrmacht straight up killed POWs or sometimes just didn't take any in the first place. The Wehrmacht also used explosive bullets against the Red Army which are prohibited same like dum dum. Soldiers were prohibited to take these bullets with them to the Western Front.
An example which shows the nature of these rules are the British commando raids. Hitler threatend to execute captured commandos the British replied by stating they would do the same with German POWs. At the end of the day nobody killed any POWs. Laws of war in a nutshell.
It should be noted that Germany was the first to oppose the usage of these type of ammunitions.
Edit: Irronically only ground troops were prohibited to use these types of ammunition. Aircraft often used explosive bullets for example and they also attacked ground forces.