From the February '99 ASC magazine:
"In fact, for one Akela shot of the soldiers climbing up the hills, we waited specifically for a light change to happen. The scene starts out in heavy cloud cover, but the sun comes out and reveals these guys sneaking through the grass. That particular light change worked well for us." John Toll, ASC
You can read the whole thing at http://www.theasc.com/magazine/feb99/war/index.htm . The specific quote is in the middle section of the third page.
I clearly remember being in awe of that shot as I was watching it in a theater back then. For a brief moment, the soldiers were kind of "safe and protected" by the relative shade, but then the sun revealed itself, striping them of their cover, and exposing them as sitting ducks in a truly hopeless situation. I seem to remember that the transition from dark to bright, was much more impressive (and menacing) on the silver screen, than in any of the subsequent DVDs that I watched. Maybe in the transfer they toned down a little bit the two extremes.