On the face of it, there doesn’t seem much involved in making a sword. Get some iron, heat it, hit it with a hammer until it is flat and shaped like a sword, stick a handle on it and sharpen the edge.

In actuality, every one of those steps is fraught with difficulty. But ultimately all the work that went into forging a sword was in answer to the fundamental paradox that lies at the heart of sword-making. A sword needs to be hard so that it can hold an edge, but it needs to be flexible so that it will not break. All the smith’s art and craft was devoted to solving this paradox.

The solution depended upon marrying iron with its closest cousin, steel.