Blu's wondering why their daily supply of timber hasn't come in a week. They soon figured out that Red has cut their supply line for themselves. Blu wants revenge on Red so they can take back their lumber. How you may ask?
Why, by pushing a highly explosive bomb past their own lumberyard that then leads into Red's open base which happens to have a bomb pit in the middle of their supply lanes that the bomb track just so happens to lead to of course.
What else whould you expect from them?