In 481 BC, after roughly four years of preparation, Xerxes began to muster the troops for the invasion of Europe. Herodotus gives the names of 46 nations from which troops were drafted.[24] The Persian army was gathered in Asia Minor in the summer and autumn of 481 BC. The armies from the Eastern satrapies was gathered in Kritala, Cappadocia and were led by Xerxes to Sardis where they passed the winter.[25] Early in spring it moved to Abydos where it was joined with the armies of the western satrapies.[26] Then the army that Xerxes had mustered marched towards Europe, crossing the Hellespont on two pontoon bridges.[27]