To summarize Clara Barton's contributions during the Civil War, the following three details should be included:
- Barton earns permission to join the army and provides supplies to soldiers in the field when supply wagons cannot get through.
- Barton convinces the army to set up aid stations near every battlefield so wounded soldiers can receive immediate medical care.
- She speaks in cities around the country to talk about the Red Cross and to encourage others to become involved.
These details highlight her direct involvement in aiding soldiers during the war, her advocacy for better medical care, and her efforts to promote the Red Cross after the war.