In the last battle of the Avatar movie, why did the general send in ground troops to engage the navi?

In the recent James Cam movie, the last battle scene included a convoy of airships escorting a bomber. In a scene earlier in the movie, this same unit attacked and knocked out a big tree the blue people really liked. We also saw that the arrows and weapons of the blue people had no effect on the airships. The last Mission was to destroy the Deity of the navi. So why were there troops dropped onto the ground? what was the point of that? the general already knew they couldn't be attacked from the ground by the navi when they were in the air. So what as the purpose there? If he had just added those troops to his convoy in the sky and ignored the navi on the ground, he would have beaten the navi because all those people and animals they gathered would have been taken out of the playing field. Did i miss something?