Slitherine

I am really new at this game, but I do have a few others, like Harpoon and Rome. I guess I'm just not understanding what I'm doing wrong but I can't meet the primary objective of linking the 2 towns. I have taken tobruk, mangled the Brits and met almost every requirement, but its just not clear to me on how to link the two targets (Sollum and El Agelia(sp.). Is it a zone of control thing? Do I have to leave a line of troops lagging behind? Not the easiest considering the Brits can use a lorry to break a zone of control. Nothing in the manual so I could use a bit of help. Thanks!

There must be an unbroken chain of own-controlled hexes between the two locations.
Sometimes the objective is set up with a green check-mark when the condition is met. but it could also be set as open (blue question-mark).
This last indicates that the final check will be done on the last turn.