The riverlords and the northern bannermen had camped at Riverrun, assembling under the call of Rose Stark. After the execution of her father she would no longer accept to be ruled by the Lannisters in King's Landing at the coronation at Riverrun Rose sits on her throne with her newly forged crown as the northern lords and riverlords raise their sword and chant.

"Queen in the north!"

The lords hail her and she looks at the hall as she now has now proclaimed herself queen and rejected the sovereignty of the Iron Throne. It wasnt a war for just revenge, but a war for independence.