160 ships according to the Anglo-Saxon chronicle In the autumn of 1016, the Danish prince Cnut the Great (Canute), supported by Eiríkr Hákonarson,[3] and Thorkell the Tall successfully invaded England.

That same summer Æthelred’s eldest son, Æthelstan died, leaving his younger brother, Edmund, as heir to the English throne.

Cnut wasted no time to prepare for the reconquest, Among the allies of Denmark was Bolesław I the Brave, the duke of Poland, (later crowned king) a relative to the Danish royal house.

He lent some Polish troops,[4] likely to have been a pledge made to Cnut and his brother Harald when, in the winter, they "went amongst the Wends" to fetch their mother back to the Danish court.

This wedlock formed a strong alliance between the successor to the throne of Sweden, Olof Skötkonung, and the rulers of Denmark, his in-laws.

In 1015, a great council convened in Oxford during which Eadric Streona, Æthelred’s son-in-law and Ealdorman of Mercia assassinated Sigeferth and Morcar, described as two of the most influential thegns of the Five Boroughs, under orders from the king.

[8] A passage from Queen Emma's Encomium provides a picture of Cnut's fleet:[T]here were there so many kinds of shields, that you could have believed that troops of all nations were present.

In late December Cnut crossed the River Thames at Cricklade pillaging and burning Mercia, including Warwickshire.

Uhtred, for unknown reasons hastened north and surrendered to the Danes, but at the instigation of Cnut he was murdered by Thurbrand the Hold due to a vendetta.

Sources on the outcome of the battle conflict, John of Worcester records this as a victory for the English while the Encomium Emmae Reginae, citing Thorkell the Tall as heading the Danish army, claims otherwise.

"Then collected he [Edmund] his force the third time, and went to London, all by north of the Thames, and so out through Clayhanger, and relieved the citizens, driving the enemy to their ships.

It was within two nights after that the king went over at Brentford; where he fought with the enemy, and put them to flight: but there many of the English were drowned, from their own carelessness; who went before the main army with a design to plunder.

(Anglo-Saxon Chronicle)" After the battle Edmund returned to Wessex to compensate for his losses, while Cnut took this as an opportunity to yet again besiege London, but he suffered too many casualties and retreated into Mercia to plunder.

According to the Anglo-Saxon Chronicle this was when Eadric switched his allegiance back to the English, and he allegedly convinced Edmund not to attack the Danes at Aylesford.

“When the king understood that the army was up, then he collected the fifth time all the English nation, and went behind them, and overtook them in Essex, on the hill called Assingdon; where they fiercely came together.

And all the nobility of the English nation was there undone!” - Anglo-Saxon Chronicle The battle is mentioned briefly in Knýtlinga saga which quotes a verse of skaldic poetry by Óttarr svarti, one of Cnut's court poets.

King Knut fought the third battle, a major one, against the sons of Æthelred at a place called Ashingdon, north of the Danes' Woods.

On an island called Olney near Deerhurst, Cnut and Edmund convinced by the nobility, met to negotiate terms of peace.

He exiled Edmund’s 2 baby boys to Sweden, to be killed by King Olöf Skotkonung, but he secretly spared their lives and sent them to Hungary, where his daughter was queen there.

Cnut built a church, chapel or holy site near the field of assandun to commemorate the soldiers who died in battle.