Why did Xerxes I have bridges built across the Hellespont?

Xerxes I had bridges built across the Hellespont to facilitate the movement of his massive army during his invasion of Greece in 480 BCE.12

As part of his extensive military preparations, Xerxes required a way to transport his troops from Sardis into Europe. He ordered the construction of two boat bridges across the strait to serve as a crossing point for his forces. Although a storm initially destroyed the bridges, they were rebuilt, allowing Xerxes to oversee the passage of his army over the course of seven days. This engineering feat was essential for the logistical support of his campaign, which included a large fleet intended to act as a supply line for the land forces.13