Arthur – Physician work
Arthur could make wounds - even fatal ones - without a thought in a battle; But he did not have the courage to mend them together.
Arthur was ashamed of it, but only the thought about pulling a needle trough someone´s skin made him nervous. He could bandage minor wounds, but if he needed to make any kind of healing salve for those wounds his hands would shake - what if he made a mistake and the wound got only worse because of him?
He had courage for bringing and facing death, but healing and fighting death trough something else than physical power was too… scary for him.
Arthur could say anything about Merlin's courage on battlefields, but he knew the truth. The truth was that Merlin was always there without the protection training gave for his knights; but also when Arthur stopped fighting Merlin would continue.
Merlin was braver than him. The boy - man - spend his days with Arthur so he couldn't have much time to actually study and learn what Gaius did. Merlin wasn't a physician but he did his best with the little knowledge he had - and he did it with confidence.
Once after a battle Merlin asked if he had ever done stitches before and held a needle and thread out for him. Arthur had frozen, his eyes wide and focused on the needle. Merlin had looked him in the eyes for about five full seconds, given Arthur a bandage, and told him to go help Gwaine with a scratch while he prepared to do those stitches himself.
Merlin never tried to give him a needle again. There were weapons in this world Arthur didn't dare to try to master. Merlin would wield those weapons for him.