Might one suggest that the selection of House Manderly as Lords of White Harbour (undercutting ‘Crusader’ rhetoric, physically blocking assaults on Northern heartlands and creating a venue for peaceful interaction) has allowed for 1000 years of cooling-off for the North/Vale rivalry? (the fact that warfare cannot have been continuous, given the lack of physical connection between both territories and the ferocity of the Northern Climate must have helped too).