He was getting on very well, when once more, close to his ear, came a sound like the crack of doom.
It was the field-guns now, and the sound of a field-gun close at hand is bad for the nerves if you aren't expecting it.

Peter thought he had been hit, and lay flat for a little to consider.

Then he found the right explanation, and crawled forward very warily.
Presently he saw his first Russian shell.

It dropped half a dozen yards to his right, making a great hole in the snow and sending up a mass of mixed earth, snow, and broken stones.

Peter spat out the dirt and felt very solemn.