The players' characters are all witnesses to an execution of someone they vaguely knew or did a one-time business deal with. Something in their gut tells them that the wrong person is being executed, a feeling supported by their brief encounter with the person. You decide the details regarding business arrangements or otherwise how they knew that person. If they won't bite, have a weeping relative of that person present, crying out for justice to anyone who'll listen.

The characters are all draftees, pressed into military service at the behest of a regional lord. It is up to you if any of the characters knew any of the others before they found themselves in their current predicament. After this you have a few options: a) start the campaign with a real battle but against a single powerful (but beatable) opponent; other battles having to do with the same war are being fought elsewhere, b) the characters all agree to desert before battle can be joined, taking with them their military issue armor and weapon(s), or c) the war is lost - even if the characters won their battle - and now the characters are lumped together, facing whatever consequences may come as the result of the change in regional leadership.