Bullets are designed to do damage, often to a human target.
Today’s invention is a new form of bullet with the opposite intent. Medics on a battlefield would be equipped with a (white+red cross-labeled) rifle. This they would use to fire a very low velocity round at soldiers who had been wounded.
The medical projectiles fired would contain anaesthetic and perhaps even some coagulent or active medicine. This would potentially allow a wounded soldier to save their own life by crawling clear of danger or stabilise them so that their retrieval could be delayed until it was safe for medics to attend and evacuate their comrade.