It's the end of World War I, and you're a world famous philosopher. Several armchair commentators have theorized that another world war may break out in a few decades, but they're not sure over what. Meanwhile, there is vigorous debate going on about just war theory, whether nations are ever justified in killing civilians, the non-aggression principle, and so forth. Most philosophers argue that war is justified under certain conditions but not under others. You are inclined to agree with them, although you disagree slightly on what the conditions are. So, what should you do?
Now, suppose you argue that war is sometimes justified and give a list of criteria, such as responding to aggression. When the Nazis take power, they will inevitably argue, as best they can, that they meet the criteria, and hence that World War II is justified. Now, world famous as you are, it will probably be difficult beforehand to anticipate exactly what the new world war will be fought over, and your criteria may be vague enough that either side can appropriate your argument. Even if you do exclude the Nazis when arguing what makes war justified, they can easily appropriate the rest of your argument and replace the things you said justify war with their own grievances. It's not difficult to take an argument saying that self-defense justifies violence and stretch it to argue that harms against the German people justify warfare. Add to this that the Nazis will inevitably lie about what's happening and invent a list of harms to justify war.
But suppose you instead argue that war is always wrong, that people should refuse to fight no matter what. If this logic becomes somewhat popular everywhere, even a little, it will make it more difficult for any aggressor to justify war. They can say that other nations are plotting against them, but if their population has a lot of die-hard pacifists, then those arguments won't do much to convince them.
Since you don't know who will listen to your arguments for or against pacifism, you should therefore advocate for violence not to be used ever, because if everyone uses violence less it will be a net gain for everyone. If the Axis powers use fewer soldiers and attack fewer civilians, and the Allies use fewer soldiers and attack fewer civilians, then the win probabilities remain roughly equal, but fewer people die.
Disclaimer: I'm actually not 100% sure if this logic holds up or not, but I thought it was worth sharing. A downside of this approach may be that lying about your conclusions leads to people accepting bad logical premises.