Short answers, pulled from the story.
The Battle of Maldon took place on 10 or the 11th of August 991, beside the River Blackwater near Maldon in Essex, England. The most likely site is the Northey Island causeway, about two miles southeast of Maldon.
Earl Byrhtnoth, an ealdorman of Essex, led the English forces at the Battle of Maldon. His troops were largely local farmers and villagers drawn from the Essex Fyrd militia, not a professional army.
Ofermōde literally means 'over-heart' in Old English, but scholars dispute whether it implies sinful pride or reckless excess of courage. J. R. R. Tolkien argued it was a condemnation, noting that in every other surviving Old English instance the word describes Satan's pride.
The poem survived because John Elphinstone, or his assistant David Casley, transcribed its 325 lines in 1724, seven years before the manuscript burned in the Cotton library fire at Ashburnham House in 1731. That transcription is now held in the Bodleian Library as pages 7 through 12 of MS Rawlinson B. 203.
The Danegeld paid after the Battle of Maldon was 10,000 Roman pounds of silver, roughly 3,300 kilograms, worth approximately £1.8 million at 2022 prices. Archbishop Sigeric of Canterbury had advised King Æthelred to buy peace from the Vikings rather than continue fighting.
One manuscript of the Anglo-Saxon Chronicle identifies the Viking leader as Olaf, possibly the Norwegian Olaf Tryggvason. The Viking force is estimated to have numbered between 2,000 and 4,000 fighting men.