Season 1 and season 6 were both about a tenuous peace, with mostly small-scale conflicts (the Battle of Winterfell being the main exception). That’s why there’s a certain parallelism with the situation going into Game of Thrones season 7 with the events of Game of Thrones season 2. Structurally, Winds of Winter was going to be the third book in the original plan, and the second to last in the six-book plan. Martin originally thought up A Song of Ice and Fire, he thought it would be three books later, it became two trilogies before expanding to the current seven-book plan.
