The Heavy Westerlander Knight is a heavy cavalry unit and is the top tier unit of the cavalry tree in the Westerland faction. They, along with the Heavy Reachman Knight, the Heavy Stormlander Knight, and the Heavy Riverlander Knight, are amongst the best cavalry units on Westeros. They have extremely heavy armor and good stats, which means that they will be strong allies or hard enemies to deal with. However, they are not invincible, as their horses are vulnerable to anti-cavalry weapons, such as the spear, the pike, the halberd, billhook, etc. They can be swarmed easily by infantry units if their horses are taken down.
One of the most effective tactics to use with Heavy Westerlander Knights is, similar to Swadian Knights in original Mount and Blade Warband, is to have your infantry hold ground and form ranks. When the enemy are advancing towards your infantry, tell your cavalry to follow you and flank to the left or right until you are behind the coming enemy. When they are within charging distance, charge both your cavalry and your infantry at the same time. Timing is vital, as ideally, both troop divisions need to hit the enemy simultaneously. This attack will greatly weaken the enemy as their attention will be split in two directions at once, halving their combat effectiveness and allowing the infantry to support the cavalry, who are vulnerable to pikemen and halberdiers.
It is recommended not to use flanking tactics on a hilly battlefield since the Knights' horses won't be able to run at full speed and will be taken down more easily. Instead, try to let the battle take place on a flat piece of ground or keep your Knights together with your infantrymen. Since most maps in A Clash Of Kings have a river in the middle, it is advisable that the player attempt to pin the enemy down in the river as they wade across, and repeatedly engage and disengage your Knights to maximize the effect of charges.