Excerpt from Joan of Arc by Helen Castor, plus links to reviews, author biography & more

That's also a difficulty for us: whether we, with the mindset of a very different age, can understand not just the finer points of late medieval theology, but the nature of faith in the world that Joan and her contemporaries inhabited. There seems little purpose, for example, in attempting to diagnose in her a physical or psychological disorder that might, to us, explain her voices, if the terms of reference we use are completely alien to the landscape of belief in which she lived. Joan and the people around her knew that it was entirely possible for otherworldly beings to communicate with men and women of sound mind; Joan was not the first or the last person in France in the first half of the fifteenth century to have visions or hear voices. The problem was not how to explain her experience of hearing something that wasn't real; the problem was how to tell whether her voices came to her from heaven or from hell – which is why the expertise of theologians took centre stage in shaping responses to her claims.

Similarly, it might seem to us as though part of Joan's power lay in bringing God into play within the context of war; that, by introducing the idea of a mandate from heaven into a kingdom exhausted by years of conflict, she made possible a new invigoration of French morale. But in medieval minds, war was always interpreted as an expression of divine will. The particular trauma for France in the 1420s was that its deeply internalised status as the 'most Christian' kingdom had been challenged by the bloodletting of civil war and overwhelming defeat by the English. How were the disaster of Azincourt (as the French knew what the English called 'Agincourt') and the years of suffering that followed to be explained, if not by God's displeasure? This was the context in which Joan's message of heaven-sent salvation was so potent, and the need to establish whether her voices were angelic or demonic in origin so overwhelmingly urgent.

And this is the reason why I have chosen to begin my history of Joan of Arc not in 1429 but fourteen years earlier, with the catastrophe of Azincourt. My aim is not to see Joan's world only, or even principally, through her eyes. Instead, I've set out to tell the story of France during these tumultuous years, and to understand how a teenage girl came to play such an astonishing part within that history. Starting in 1415 has made it possible to explore the shifting perspectives of the various protagonists in the drama, both English and French – and to emphasise the fact that what it meant to be 'French' was profoundly contested throughout these years. Civil war threatened France's identity geographically, politically and spiritually; and Joan's understanding of who the French were, on whom God now intended to bestow victory through her mission, was not shared by many of her compatriots.

What follows is an attempt to tell the story of Joan's France, and of Joan herself, forwards, not backwards, as a narrative in which human beings struggle to understand the world around them and – just like us – have no idea what's coming next. Of course, in the process I too have had to pick my way through the evidence, choosing what to weave into a seamless story; but in the notes at the end of the book I've tried to give a sense of how and why I have made my choices, and where the pitfalls might lie within the sources themselves and in the testing process of translation from the Latin and French in which most of them are written. Among all the challenges presented by this mass of material, the most difficult is dealing with the trials, which were defining events in Joan's life and afterlife at the same time as providing evidence through which to interpret them. My aim has been as much as possible to let them take place as events in Joan's story – in other words, to allow the testimony of Joan herself and of the other, later witnesses unfold as it was given and recorded, rather than to read their memories and interpretations backwards into the earlier events they were describing.

From Joan of Arc by Helen Castor Copyright © 2015 by Helen Castor. Reprinted courtesy of Harper, an imprint of HarperCollins Publishers.