tlb wrote:I consider the L1 and L2 points to be in the neighborhood, there is no requirement that they actually orbit the planet.
The problem with those Lagrangian points is that they're useful for other things too. The L1 point has an unobstructed view of the star, so it's an ideal location to place energy-intense industries. It would also place any installation there 5 light-seconds away from the planet and thus that much further from any enemies. FTL comms negate some of this, but you'd want to reduce the failure modes if you can.
L2 makes a bit more sense for that reason and because you wouldn't place energy-intense industries there... but you may want to instead place cold industries.
In any case the original post could be interpreted as questioning whether any forts existed that were assigned to the planets and not just for the junction. The quoted text clearly indicates that such forts exist.
The best indication we have of what MDM-based defences would be is Bewoulf. During Operation Fabius, we saw them preparing to launch and then launching. There's no indication those people were on-board a fort around the planet. (It also shows the fragility of FTL links)
But I don't think it makes sense to have
forts if they are not in orbit of the planet. You can have an armoured control centre off planet, but that's not the same as a fort. In my mind, a fort must be able to contribute with energy weapons if push comes to shove (that makes sense around the Junction), but maybe the GA planners have concluded that if the shoals of MDMs have been exhausted and the enemy is within energy range of where the forts would be, all is already lost anyway.