The Persian ruler Xerxes would have never claimed to be a god. He was a Zoroastrian who believed in a monotheistic and supreme creator god. Also, there were way more than 300 Greek forces at the battle of Thermopylae. Try 4,000. Likewise, the Persian numbers were exaggerated. Historians believe they were likely more around 70,000 to 300,000 rather than 1,000,000.