I know the story of Joan of Arc very well and I know that she is considered to have had an unmeasurable effect on the development of French nationalism. Where I have trouble is making the connection of how her actions lead to nationalistic fervor. Any thoughts?
Clearly Joan of Arc has become a symbol of French nationalism and one that has been used by the various powers that be, as sagesource identifies in #3. It is interesting how other political figures outlive themselves and become symbols of other things, depending on the various powers in charge and the political situation. Consider how Guy Fawkes has become a symbol in Britain of treason. Hardly fair on the poor guy as he was just one of many anti-regency plotters!
Actually Joan of Arc did not stay entirely true to her beliefs. She confessed at one point and "repented," and was sentenced to life imprisonment. However, her captors were so intent on killing her that they allegedly tricked her into wearing male attire again in prison (supposedly, she was left with the alternative of either wearing men's clothing or going to the bathroom naked). This was a transparent excuse to execute her rather than let her live as a prisoner, but it backfired. Since she was lost in any case, Joan retracted her confessions and defied the court, consequently being excommunicated and burned at the stake.
In the nineteenth century, Joan of Arc was revived as a hero and martyr by the French Church. Her elevation as a saint was primarily a political move to enhance the political chances of the clerical parties in France, and to "advertise...the intimate union between patriotism and the Catholic faith," as the 11th edition of the Brittannica encyclopedia put it. She became a successful and popular symbol for other groups because she was a woman, a resistance fighter, a member of the lower classes, and (for monarchists), a supporter of the king. As with all truly popular symbols, Joan of Arc thus speaks with a multitude of voices, depending on the listener.
Part of it probably comes from the hatred that the French and English have for each other. Joan of Arc was burned at the stake by the English, but she stayed true to her nationality and her religious beliefs. Her honor, her courage, and her ability to face the adversity of the English in the face of death, and her youth (she was only 19 when she died) all help to make her an unbeatable French icon.