In the event of combat and wounded and dying men, HMS Belfast has its own surgical theatre. The goal would be to stabilize a patient until they could be transferred to a hospital ship or shore station, not perform complex procedures.
I don't know about HMS Belfast, but on some smaller US Navy ships, medics would perform open surgery when doctors were not available. Some medics were so skilled after years of combat that doctors would not even bother to supervise them during amputations, sutures, and other emergency procedures, instead focusing on the critically wounded.
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