Apolgises for bad picture, but you can see it in the game, middle of contemp map on the left.
Just clicked on the process:
The guild is a hankook spin off and Hankook took sector 54,50 to open up the top and last landing zone, Hankook's ghost/sister guild then siege the landing zone and take it and then push north giving up sectors behind them, once they are far enough away to release the sector that opens the landing zone then Hankook releases their sector which originally opened it and no ones else can follow them.
Pretty clever and my hats off to them as they can repeat this as many times as they like.