[Ares]

First thing I would do is immediately downgrade your treaties with both. If they were human, I'd tell them that, although I bear no hostilities toward either of them personally, I cannot allow them to use me to further their war with each other. Remember, they're not just using your supply depots, but also you intelligence points (though I know the AI doesn't use it effectively, but still...), as well as you vision. This war is between the two of them. If they wish to pursue this war for their own honour, you (being both warrior and honourable yourself) must respect that, although you can, of course, refuse to be a part of it. You can (and perhaps should) continue to plea with them for peace, but if they feel they have been dishounored, you must, in the end, give them a chance to reclaim that honour.