Answer:
William used the tactic of a false retreat in an attempt the break the shield wall and lure English troops off the ridge. Harold's brother Tostig, joined forces with Harald Hardrada. The wind changed direction allowing William to sail to England when Harold was in the north defeating Harald Hardrada.
Step-by-step explanation:
William changed his tactics and moved his archers from the front of the battlefield to behind the infantry. The change in position of the archers meant that, rather than flying over the heads of the horsecars, their arrows hit the Anglo- Saxon army squarely and caught them by surprise.