I once participated in what I would describe as a broadly anti-war activist coalition that drew its membership almost exclusively from left-liberal and socialist college kids.
My experience was an abundance of meetings, a small handful of rallies and demonstrations (which were largely disappointing), and no impact whatsoever on the war in question. After a while, the group in my city was increasingly dominated by two competing communist groups, and sort of dissolved as people either joined those groups or stopped participating (mostly the latter).