How does Bernard Cornwell use imagery in Sharpe's Regiment?

Imagery:

"Sharpe was staring into the ruin of the Sergeant Major's belly. MacLaird's filthy shirt had been driven into the wound that welled with gleaming, bright blood. Sharpe let the jacket fall gently onto the horror. There was nothing to be done."

"He was speaking as if he had been there, in that valley of the Portina where the wounded sobbed for mercy. There had been small black snakes, Sharpe remembered, wriggling away from the grassfires. His mind seemed a whirl of black snakes, memories, and sudden shock because his journey had been useless."