Question: Æthelwulf of Berkshire (before 825 – 4 January, 871) was a Saxon ealdorman, he received a land grant in 843/44 from Brihtwulf, king of Mercia; and lost his life at which battle event?

Context paragraphs:
Æthelwulf of Berkshire: Æthelwulf of Berkshire (before 825 – 4 January, 871) was a Saxon ealdorman.  In 860 he and other men of Berkshire fought off a band of pirates near Winchester, Hampshire.  Later he mustered a force of 1400 men against an army of Danes, won the 31 December 870 Battle of Englefield on behalf of the then kingdom of Wessex.  He received a land grant in 843/44 from Brihtwulf, king of Mercia; and lost his life at the Battle of Reading.

Battle of Reading (871): The first Battle of Reading was a battle on 4 January 871 at Reading in what is now the English county of Berkshire.  It was one of a series of battles, with honours to both sides, that took place following an invasion of the then kingdom of Wessex by an army of Danes led by Bagsecg and Halfdan Ragnarsson in an attempt to conquer Wessex.  Both battle and campaign are described in the "Anglo-Saxon Chronicle", and this account provides the earliest known written record of the existence of the town of Reading.

Æthelwulf: Æthelwulf (Old English for "Noble Wolf"; died 13 January 858) was King of Wessex from 839 to 858.  In 825, his father, King Egbert, defeated King Beornwulf of Mercia, ending a long Mercian dominance over Anglo-Saxon England south of the Humber.  Egbert sent Æthelwulf with an army to Kent, where he expelled the Mercian sub-king and was himself appointed sub-king.  After 830, Egbert maintained good relations with Mercia, and this was continued by Æthelwulf when he became king in 839, the first son to succeed his father as West Saxon king since 641.

San Miguel del Vado Land Grant: The San Miguel del Vado Land Grant (also known as the San Miguel del Bado Land Grant) is one of the northern Spanish land grants in New Mexico.  The original grant was lost, but a second grant was obtained by 58 men and their respective families on March 12, 1803.  Two days later, the procedure was repeated at San José del Vado, three miles upstream from San Miguel, distributing farm land to an additional forty-seven heads of household, including two women.  Fifty-three men had earlier submitted the petition, and were granted temporary possession on November 24, 1794, pending satisfaction of prescribed criteria.  Thirteen of the original men who applied for the grant were genízaros, those Native Americans, captured or sold into slavery, some of whom had complained of poor conditions and were granted lands by the governor for farming, often to provide a buffer of protection for larger towns, such as Santa Fé, against enemies.  In 1896, the Supreme Court ruled in "United States v. Sandoval" that the grant would be reduced from the surveyor general's estimated 315,000 acres, including common lands, to the little more than 5,000 acres then under private ownership.

Bagsecg: Bagsecg (also known as Bægsecg or Bagsec) (died 8 January 871) was a Viking leader commonly referred to as a king.  In 870 or 871 he led The Great Summer Army to England.  His forces joined those of the Great Danish Army which had already overrun much of England.  He and Halfdan Ragnarsson became the leaders of a joint invasion of the Kingdom of Wessex.  He was killed at the Battle of Ashdown, fighting a West Saxon Army led by King Ethelred and his younger brother, the future Alfred the Great.

Battle of Stamford (894): The First Battle of Stamford occurred when West Saxon Ealdorman Aethelnoth invaded the town in the summer of 894, but it was not besieged and Danish rule was unaffected.

Ealdorman: An ealdorman (from Old English "ealdorman", lit.  "elder man"; plural: "ealdormen") was a high-ranking royal official and prior magistrate of an Anglo-Saxon shire or group of shires from about the ninth century to the time of King Cnut.  The term "ealdorman" was rendered in Latin as "dux" in early West Saxon charters, and as "præfectus" (which is also the equivalent of "gerefa", modern reeve, from which sheriff or shire reeve is derived).  In the "Life of King Alfred" by the Welsh bishop Asser, the Latin equivalent is "comes".  As the chief magistrate of a shire or group of shires (county) in Anglo-Saxon England, he commanded the army of the shire(s) and districts under his control on behalf of the king.

Æthelfrith of Mercia: Æthelfrith (fl.  880s – c. 904/915) was an ealdorman of southern Mercia, who flourished in the last two decades of the ninth century and the first decade of the tenth century.  His father is unknown.  He was married to Æthelgyth, daughter of Æthelwulf; Æthelwulf is unidentified, but a possible candidate is King Alfred the Great's brother-in-law, the ealdorman of the Gaini who died in 901.  Æthelfrith was father to four ealdormen: Æthelstan Half-King (East Anglia), Ælfstan (Mercia), Æthelwald (Kent), and Eadric (Hampshire).

Battle of Ellandun: The Battle of Ellandun or Battle of Wroughton was fought between Egbert of Wessex and Beornwulf of Mercia in September 825.  Sir Frank Stenton described it as "one of the most decisive battles of English history".  It effectively ended Mercian Supremacy over the southern kingdoms of Anglo-Saxon England and established West Saxon dominance in southern England.

Æthelswith: Æthelswith (c. 838–888) was the only known daughter of King Æthelwulf of Wessex.  She became Queen Æthelswith when she married King Burgred of Mercia in 853.  The couple had no issue.  Her marriage probably signalled the subordination of Burgred to his father-in-law and the Saxon kingdom at a time when both Wessex and Mercia were suffering Danish (Viking) raids.  Burgred also had ongoing problems with the Kingdom of Powys on his western border and in 853 Æthelwulf subjugated the Welsh state on Burgred's behalf.

Supporting paragraphs: Æthelwulf of Berkshire Battle of Reading (871)
Answer: Battle of Reading