Even if they did not undertake to storm the fort they would linger near it, in the hope of cutting off men who came forth incautiously, and at night, especially if it happened to be dark, they would be sure to come very close.
The palisade was about eight feet high, and the men stood on a horizontal plank three feet from the ground, leaving only the head to project above the shelter, and Willet warned them to be exceedingly careful when the twilight came, since the besiegers would undoubtedly use the darkness as a cover for sharp-shooting.

Then both he and Robert looked anxiously at the sun, which was just setting behind the black waste.
"The night will be dark," said the hunter, "and that's bad.

I'm afraid some of our sentinels will be picked off.

Robert, you and I must not sleep until tomorrow.

We must stay on watch here all the while." As he predicted, the night came down black and grim.