sometimes things are out of your hands, like when russia invades ukraine.
recall that i was responding to someone saying that anti-war folks are actually pro-genocide and anti-west. so, from the anti-war perspective, if what you want is peace, (which is what anti-war means), then "arming ukraine for a decisive victory" is what, exactly? it's giving ukraine weapons, or, to put it in other words: it's giving money to weapons manufacturers.
if you think giving money to weapons manufacturers will lead somehow to peace, then i don't know what to tell you.
you could shorten the war by aiding russia, but obviously no one wants that. that would genuinely encourage violence, like when the united states aids saudi arabia against the people of yemen.
since the rest of the world can't make choices on russia's behalf, the only thing to be done, from an anti-war perspective, is to mitigate the damage russia does to ukraine, and encourage, through non-violent means, a cessation of violence.
arming ukraine is the opposite of that.
what else could the united states do? (or whatever country, i'll just go with the united states for the sake of brevity.) the united states could invade ukraine too, to counter russia. would that end the russia-ukraine war? no, it would just start the america-russian war.
all i'm trying to convey is that anti-war people are, probably, for the most part, actually just that. conversely, if you're pro-ukraine, or anti-russia, or anti-ukraine, or pro-russia, you are, probably, for the most part, actually not anti-war. you have other priorities, which is your business, not mine. but i won't just be called pro-genocide by someone who's gotten themselves all worked up into a froth for war.