He knew the work, and rejoiced in it.
This was why he was a soldier.

Silently, swiftly, he unbuckled his belt, refastening it across the straps so as to hold canteen and haversack noiseless, and then, revolver in hand, began creeping down under cover of the low banks.

He must explore the path first before attempting to bear her along in his arms; must be sure the passage was unguarded.

After it swerved to the right there would be little danger, but while it ran straight, some cautious savage might have chosen it to skulk in.

To deal with such he needed to be alone, and free.
He must have crawled thus for thirty yards, hands and knees aching horribly, his eyes ever peering over the edge of the bank, his ears tingling to the slightest noise.