I wonder why Balon attacked the North.
The move was non-sense by many aspects:
1 The North and the Stark don't have a huge fleet, or at least it is in White Harbor very far away, so it wasn't a threat to his kingdom. The Lannister and the Tyrrels were a bigger threat
2 The fish villages and cities on the coast were poor. The only rich castle is Winterfell, but he actually didn't planned to attack it
3 Lannisters are enormously rich and fighting a war on many fronts, so it would have been a rich prize with small risks
4 House Stark didn't smashed the first Balon Rebellion, it was maily due to Stannis and the Royal fleet. Ned Stark only fostered Theon, so there is no revenge against them
5 By attacking exclusevly the North they made Robb very weak and ultimately caused Roose Bolton to plot against King Robb and to the Red Wedding
(Sorry for any mistake in my writing as English in not my mother tongue)