When you retreat to the west part of the room, the north Gentryii attached to the wall will form a V-shape, causing its chain to go diagonally for 3 squares no matter where the head drags its nearby chain after that.
Getting the other Gentryii to cooperate to close the gap is a little tricky, and involves using your sword to manipulate its brained movement so it drags its chain to a convenient spot. Then when you drag it down and trap it on the door, its tail will be adjacent to the kink in the north Gentryii's tail.
Soldier calls can't pathfind through diagonal chains, of course.
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