So I re-watched Avatar 1 and I was struck by a question. What was the point of the ground forces in the Assault on the Tree of Souls?

The aircraft drop them off at the start of the battle, but after that enter formation and proceed to advance far faster than the ground units and over terrain that wouldn't be easy for ground units to cross.

The Na'vi still engage them, which means either:

A: There was a significant number of Na'vi who were only cavalry, but if that's the case why would the RDA bother fighting them? Just let the cavalry run around on the ground being useless and keep the infantry on choppers as extra firepower and the AMPS in reserve to deploy nearer the target.

B: The RDA deployed ground forces to force Sully to keep a significant number of Na'vi on the ground and not on Ikrans to take pressure off the aircraft. Except this requires Sully knowing the RDA was going to deploy ground forces miles from the battle, and then for Sully to decide to deploy a significant number of Na'vi as ground forces instead using them on Ikrans,