BD Chapter 11. The Two Things at the Very Top of My Things-I-Never-Want-To-Do List

Told you there were still bigger changes ahead for Jacob. 

Key Plot Points fromThe Twilight Saga: The Official Illustrated Guide

• Jacob struggles against Sam's order to obey
  Jacob is the true Alpha -- he was not born to kneel to Sam
• Jacob breaks from the pack; he will stand between the pack and the Cullens
• Jacob leaves to warn the Cullens
  Seth breaks from the pack and joins Jacob; they patrol the Cullens' land
• Bella's condition worsens

So now he's struck out on his own with Seth following, all to protect Bella and the Cullens. Edward doesn't take lightly the sacrifice that Jacob has made. The situation is definitely tenuous.