Lidgar
Gongfarmer
One thing to consider in running a "doomed" campaign is to make sure it doesn't feel too much like a railroad for the players. Remember that the Spartans on reach were in the military and on a mission - they were trained to follow orders and see the mission through. Not all (and in my experience, few) PC's act this way.
Making it evident that different actions - including "running away" and somehow avoiding their "fates" - are real options for them. This will hopefully reinforce the feeling that they are making a "willing" sacrifice, and therefore lead towards a more heroic ending to the campaign.
In addition, it should become evident through their actions that the forces of Good (or whatever forces they are representing) have the best chance for victory if they see things through to the end. Dropping clues along the way as the campaign develops can foreshadow their potential doom while adding a certain amount of desirable tension.
Making it evident that different actions - including "running away" and somehow avoiding their "fates" - are real options for them. This will hopefully reinforce the feeling that they are making a "willing" sacrifice, and therefore lead towards a more heroic ending to the campaign.
In addition, it should become evident through their actions that the forces of Good (or whatever forces they are representing) have the best chance for victory if they see things through to the end. Dropping clues along the way as the campaign develops can foreshadow their potential doom while adding a certain amount of desirable tension.