Yet another question regarding convoys

[Vichyssoise]

Apologies for starting yet another thread on the subject.

In my current 10.0 game against the AI, I declared war on Saudi Arabia to stop the convoy lane to the USA. I've controlled the port (Al Qatif oil) it starts from for a couple of turns now to no avail.
What are the required conditions to make that particular convoy lane inactive?

2 things I should mention:
a. A Saudi garrison unit is still parked in Al Qatif town (next to the port that my corps unit is occupying).
b. I have yet to take Riyadh which means that I'm still at war with SA.

[BillRunacre]

Hi

If the port the convoy runs from is still in Allied hands, as suggested by your post, then the convoy will continue to run.

Either capturing that port, or the enemy capital and making Saudi Arabia surrender, should stop the convoy.

Bill

[Vichyssoise]

Actually, I control the port the convoy lane is running from, but not the adjacent town where a unit is garrisoned.
I guess that I've got to take it too then, which makes sense.