Why did King Harold want to kill the baby Jesus? The short answer is that he didn't. The misunderstanding is due to a sleep-deprived grad student from 1964 who mixed up assignments from his British history, astronomy, and Bible classes.
It all starts with King Harold Godwinson, who was the last crowned Anglo-Saxon king of England. He was coronated on 6 January, 1066, the day after his brother-in-law Edward the Confessor died, and reigned until his own death at the hands of William the Conqueror on 14 October, 1066.
It is posited that Harold's quick coronation was possible because the noblemen were in the area for Epiphany, but that is the only legitimate part of Harold's reign. Edward's choice for a successor was not clear, and at least two other men, Harald Hardrada of Norway and then-Duke-later-Conqueror William II of Normandy, thought they were Edward's heirs. Harald had the support of Harold's brother Tostig. Edward claimed that when Harold shipwrecked on French shores in 1064 he swore fealty to Edward.
And so, a minute after Harold was crowned, Edward had 700 warships and transport ships built which sat in French harbors for seven months because the winds were bad. Harold posted troops in defensive positions—troops who spent the next seven months slowly starving to death. Eight September was a busy day as Harold withdrew his forces and Harald Hardrada and Tostig invaded at the mouth of the Tyne. Harold's army got a snack and force-marched to Yorkshire where they wiped out the invaders, including Harold's brother.
On the 12th, William's fleet finally set sail whereupon they lost several ships in a storm. Harold turned his army around and the Battle of Hastings was met on 14 October. Nine hours later, Harold Godwinson was dead and his army defeated.
The year 1066 was
also noted for the appearance of Haley's comet. Because of the timing, it was known as the "Great Easter Comet." Harold believed it was a bad omen, and indeed, it is immortalized in a tapestry commissioned by William's wife, Queen Matilda, commemorating the Norman victory.
Anyway, the grad student confused Godwinson with
God's Son, the Great Easter Comet with the star of Bethlehem, and "King Harold" with Herod the Great. The grad student's TA thought the paper was funny. She pointed out that, at this point, Jesus hadn't been a baby for over a thousand years, and if
Herod the Great couldn't kill Him, some Anglo-Saxon king who couldn't hold the crown for even a full year wouldn't be able to.