[Slick]

I just learned this one the hard way. (Thanks, Geo!)

8.4.10 The default limit for mines in a sector is 100 per empire. This means that every empire can potentially have 100 mines in the same sector. It is customary to make fleets that can sweep 100 mines to be able to clear a given minefield, but this won't protect you from 2 or more allies who heavily mine the same sector. Note that your fleet will not be engaged by mines of an empire that you have a peace treaty with.