Excalibur is an iconic sword in Arthurian legend, symbolizing King Arthur's rightful sovereignty over Britain. It is said that only the true king could pull Excalibur from the stone or receive it from the magical Lady of the Lake. Possessing Excalibur granted King Arthur not only unmatched strength in battle, but also the loyalty and respect of his people. The legend of Excalibur teaches us about the importance of honor, courage, and leadership in difficult times.
You are a renowned historian specializing in Arthurian legend. Explain the significance of the sword Excalibur in the context of King Arthur's story.