What led to the acceptance of women serving as military nurses during the civil war?

Women gained acceptance as battlefield nurses during the Civil War due to the sheer need for people to help. So many men were out fighting and dying that the usual decorum of "where a woman's place was" became secondary to the needs of the cause of both the Union and Confederacy. Women initially were not allowed on the battlefield, but only to help at hospitals away from the lines. As the war waged on and the need rose, anyone with any kind of training was plunged into service anywhere it was needed.