After reading the letter, Yu Lin Bloodhawk understood all of Sylvanas's battle plans, as well as what she was really thinking. That girl had clearly done this on purpose. All her talk of taking revenge on the centaurs was nothing more than an excuse.
They could take revenge on the centaurs of Kolkar Ridge at any time; even delaying it a few days would make no difference. And although trapping every invading centaur in the valley was an essential part of Sylvanas's military plan, it was not her entire purpose.
For that, she had no need to take every member of the Frostwolf Clan Regiment. Half would have been enough. Yet she had even taken the only Wingblade Cart they had brought into the valley!
She had said herself that she would not stop the centaurs from entering the valley, only from escaping it. Wasn't her meaning obvious? His six hundred or so soldiers of the City Lord's Household Guard would have to deal with every invading centaur themselves, while her forces stood by and watched. Unless the centaurs changed their minds at the last minute, turned around, and forced their way through the valley entrance to escape, she would do nothing.
Perhaps Sylvanas was giving Yu Lin Bloodhawk a chance to command a battle personally, and the City Lord's Household Guard a chance to gain combat experience. But Yu Lin Bloodhawk preferred to think she was shirking her responsibilities and making trouble for him.
Still, even if this was trouble Sylvanas had left him, Yu Lin Bloodhawk had no choice but to accept it.
So they needed to stake down plenty of Horse-Trip Wires! They needed to dig plenty of Horsefall Pits, too! In short, they could never have too many of either in front of the five Crossbow