Due to some long-running troubles in my campaign, I now have an orc horde of about 900 heading towards a newly-made keep town. My players have 1st level characters they are starting, and I would like to involve them in the battle. The orcs are not going to be dissuaded, nor will 5 1st-level characters do much against them directly. But reading through the Heroes of Battle book, I know that there are a lot of little ways that a small and low-level party can truly feel involved in a major war.
Sadly, I can not think of a good one. I thought of them holding a broken gate, so that orcs can only make it in a few at a time. This would be over quickly, or else the party would be overwhelmed, and I doubt it will be greatly involving for them. Does anyone have any thoughts on this?