from this position in the grove, as troops held in reserve, what do Henry and his comrades observe?

The new regiment is now halted just inside a grove of trees, facing out into a field covered in smoke. They talk about rumors and reports from battles, who has lost what and moved where. As always, there is a disagreement about what has actually happened, this time to a Union battery. The Union troops in the field of smoke begin to run. A shell screams overhead the new regiment, landing in the grove and throwing up a shower of pine needles.