France 14 question

[alaric99x]

Can anyone provide any enlightenment on how to handle the situation of the French 18th Div, orphaned at quite some distance from its parent 9th Corps in the early campaign? Is it advisable to use precious rail capacity to move the 18th toward Sedan, or should they just spend a week on the long road march? Maybe it's better to just put them on the battle line where they're presently located(?) As far as I'm aware, there's no way to attach them to any other Corps or Army, or am I wrong in assuming that? Any suggestions from someone more experienced with this scenario?