Who is Belle Block from Flags of Our Fathers and what is their importance?

When Belle Block saw the photograph of the flag-raising on Iwo Jima, she was sure that the one Marine was her son, Harlon, even though she could only see his back. Harlon died shortly after the photograph was taken and another dead soldier was incorrectly identified in Harlon's place as a flag raiser. Belle stuck to her belief that Harlon was in the photograph and was proved right several years later.