Answer:
The narrator may also be referring to how the men may have behaved.
Step-by-step explanation:
Aside from physically carrying something, the term "carrying oneself" refers to how one portrays themself to others.
Body language, grooming, and facial expressions are all examples of how someone carries themself.
In other words, aside from referring directly to how the men marched and had heavy loads, the narrator may also refer to how the men conveyed themselves.