LOL at everyone disrespecting LittleFinger (LF), they just don't know...
I think LF is going to be the one to sit on the Iron Throne at the end of the series.
You guys think LF is going to try to take WinterFell when Jon leaves?
Even though the North is the largest territory in Westeros, their army have to be depleted at this point.
Fighting the Lannisters, getting slaughtered at the Red Wedding, some Stark-loyal houses probably participated in Stannis' failed Winterfell seige, and the Battle of the Bastards are all events that support this depletion theory.
The Wildlings were sent as scouts for the White Walkers, so they are unavailable.
On the other hand, the Knights of the Vale haven't been doing shit this entire time and probably suffered minimum lost in the Battle of the Bastards.