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?

Red cross nurse uniform hi-res stock photography and images - Alamy

Nursing Uniforms of the Past and Present – Nurse Uniforms History

The History of White Nurse Uniforms - BoardVitals Blog

Dr Nigel Taylor MSc, BSc(Hons)ChEHO MREHIS, GradIOSH on LinkedIn

WW2 German DRK nurses uniform German red cross nurses uniform

See how vintage nursing uniforms evolved from starched whites to

Hungarian red cross nurse uniform hi-res stock photography and

Canadian Red Cross nurses watching the ceremony as the new

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

Red cross nurse uniform hi-res stock photography and images - Alamy