One of the greatest military campaigns ever conducted was the Persian invasion of Greece in 480 BC. King Xerxes (the ruler featured in the pages of the Old Testament book of Esther) set out to redress the humiliation suffered by his father's army at Marathon, where a small Greek force had worn out the massive Persian onslaught and whimpered it into retreat. While the previous force had been huge, Xerxes' collected battalions were massive. Historians who traveled along to document the planned Persian victories claimed that it took seven days for the entire company to pass by any one point.

When the Bosporus waters stalled the entourage, Xerxes commanded his engineers to float a bridge over the gap. But when their temporary pontoon structure was ready, the fickle European weather turned and…