Hi, I think I wouldn't worry too much about the warp effect on a planets gravitational accumulation. Ships are small relative to planets (except forEE Doc Smith's stuff) so it's likely that the warp field they generate would also be relatively small. In order for a warp field to do as suggested, it would have to significantly warp spacetime over a significant portion of the planet. But in any case you could simply use some sort of handwavium to explain that ships can't use warp drive in a gravitational field and problem solved. As to your war, if both sides have planet busters then you end up with a MAD - Mutually Assurred Destruction scenario where neither side can afford to launch. That doesn't mean there can't be accidents etc which would escalate to galaxy war one. But the real issue you have is why the war at all? If this is a crusade of some sort for one race - religious or idealogical or what have you - then you're talking fanatics. And fanatics would launch. Death be damned! And if it's not then what are they fighting over? There are two hundred million stars in the Milky Way give or take - plenty of resources for everyone. Likewise territory isn't much of an issue either for the same reason. Not if they have a drive that can carry them across the galaxy in a month. And do these races even breathe the same air etc? The very scale of these races' FTL drive makes most scenarios for war unlikely if they each only have a dozen or so planets. Now if they had tens or hundreds of thousands of worlds each, that would be something else. But as it is you're talking about two races each with a dozen marbles or so, in a country. They would hardly ever interact with one another. Cheers, Greg.