Why do older images of nurses' uniforms have a red cross?

The nurse depicted in Banksy's Game Changer artwork bears the red cross emblem - but why?

My 1940s Red Cross uniform + nurses cape! : r/VintageFashion

A Universal Code: Nurse Uniforms of All Nations – Circulating Now

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Evie (@evie__bruce) / X

Why do older images of nurses' uniforms have a red cross?

Clara Barton's crusade to bring the Red Cross to America

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WWII Red Cross and Army Uniform Exhibit – The Pragmatic Costumer

The Importance of Quality Nursing Uniforms

UNIFORM CRAFT Female Nurse Uniform | Hospital Staff, clinics, Home Health, Nanny Uniforms for Women made of Polyester-Cotton (M, Violet and Grey)

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Nurses Working Uniform, Short Sleeve Pockets Workers Tee Shirt / Top For Adults

Pocket Nurse Uniform T-Shirt Pant Coverall Workwear Suit V-neck Scrub Suit Women