I’ve been saying that Northern feudal politics are just as complicated and ruthless as Southern feudal politics since Bran VI of AGOT. Leaving aside the manifest disloyalty of the Boltons and the Karstarks as shown in ASOS and later, we can see from the Hornwood Crisis in ACOK that the lords of the North are constantly jockeying for position and power and that the Stark in Winterfell has to work very hard indeed to keep the Manderlys and the Umbers or the Glovers and the Tallharts working in harness.