Welcome to Backgammon. The standard rules of Wargear are applied.
You can attack from the top of each stack to the bottom of each partnering stack. The two stacks on each end can attack the opposite stack on the board. Although the two (2) stacks attack at a significant disadvantage, 3v6.
Bonuses are had by obtaining each stack on the board.
There are a limited number of attacks so beware of how you use them.
You may return to attack after fortify.
Enjoy!