It seems a common theme that whenever Rob, Balon or war in general is mentioned Balon is dismissed as an idiot for attacking the North instead of Allying Rob and I just can't wrap my head around the thinking there.

1. The North has no fleet whatsoever. Worst comes to worst and Ironborn are completely mauled to the man on the mainland, the Northerners have no way whatsoever of retaliating against the homeland. Tywin, The Reach, the Seven Kingdoms and Stannis would make it their lifes mission to exterminate his house root and stem and have both the means to do so and infrastructure to build a fleet.

2. The North can be accessed by only a singular chokehold, trough the Moat, which the Ironborn sucesfully took and held until the captains abandoned it when Kingsmoot was called after Balon was murdered. The Northern army was unable to pass or take it as was anyone else. It was surrendered by remaining garison trough treachery of Theon. No other kingdom, save the Vale, which is on the other side of the continent, is not engaged in war and is able to defend the Bloody Gate has anything similar. The Ironborn would be forced to lay sieges to castles while dividing their forces and exposing their flanks to enemy attacks wether they attack Westerlands or the Reach.

3. The North is poor? Being poorer than the other kingdoms doesn't make it poor. To get the wealth of Casterly Rock one must take a castle that was never taken by storm, to seize the wealth of the unprotected North one only needs to hold the Moat while the Northern army was south of it, which it was, and let Tywin, Stannis or anyone else handle the actual fighting and bleeding against said army. A bird in a hand is better than two on a branch after all.

4. Vengeance is stupid? But not when it comes to Rob or other characters driven by it. Avenging his father and family against Lannisters is great. Retaking the Iron throne you never even saw is amazing if you're Dany. But seeking independence and revenge isn't?. Theons taking of Bran and Rickon is horrible but the same being done to Theon means Theon owes eternal loyatly to the Starks. Ned would've decapitated Theon if Balon ever rose again. He always was a hostage and owed nothing to the Starks.

5. The alliance with the north is worthless. North and Riverlands have no loyalty to Iron Islands or bonds that would keep them in the war for a second longer for Iron Islands sake if they achieved their own goals, leaving Balon holding the bag. They have no fleet to come to his aid if islands are attacked and under siege. Both those kingdoms are already losing and are doomed to lose.