1066 – Battle Of Stamford Bridge, Yorkshire. The equally important, in many ways more important – precursor to the Battle of Hastings and the Norman invasion of England.
An English army under Harold Godwinson, elected King of England, defeated a Norwegian invasion force commanded by Harald III of Norway.
Three days later, the Normans landed on the south coast, and the remnants of the English force had the long march south to meet them. If they hadn’t had to deal with Stamford Bridge and a few hundred miles of forced marching, the outcome of the Battle of Hastings would probably have been quite different.
Interesting to speculate what might have happened if the Norwegians had won at Stamford Bridge, since it would effectively have left three armies in the field – the Norwegians in the north, the Normans in the south, and the remnants of the English army plus whatever back-up they could draw on from the further-flung counties. Whatever, history would tell quite a different story.