Given that the Ironborn attack on the North had clearly been in the works for several months by the time Theon returned home, do you think Balon probably started plotting it when Ned rode south?

In a passive sense, I think he’d been planning it from the moment he bent the knee to Robert Baratheon.

In an active sense, I think he’d been organizing his attack the moment that fighting broke out between Lannisters and Starks.