Aetheflaed comes to mind if for no other reason than that she militarized bees.
Æthelred died in 911 and Æthelflæd then ruled Mercia as Lady of the Mercians. The accession of a female ruler in Mercia is described by the historian Ian Walker as "one of the most unique events in early medieval history".
Alfred had built a network of fortified burhs and in the 910s Edward and Æthelflæd embarked on a programme of extending them. Among the towns where she built defences were Bridgnorth, Tamworth, Stafford, Warwick, Chirbury and Runcorn. In 917 she sent an army to capture Derby, the first of the Five Boroughs of the Danelaw to fall to the English, a victory described by Tim Clarkson as "her greatest triumph". In 918 Leicester surrendered without a fight. Shortly afterwards the Viking leaders of York offered her their loyalty, but she died on 12 June 918 before she could take advantage of the offer, and a few months later Edward completed the conquest of Mercia. Æthelflæd was succeeded by her daughter Ælfwynn, but in December Edward took personal control of Mercia and carried Ælfwynn off to Wessex. Wikipedia
The British History Podcast has an excellent couple of episodes on Aetheflaed. Jamie is clearly a fan, but I believe BHP presents evidence fairly, documenting what is certain and what is under debate. Highly recommended.
OP asks whether there is evidence that Aetheflaed commanded in the field; the BHP covers this. We don't have enough evidence to reach a positive conclusion, but the preponderance of evidence suggests that she did (from memory, she was in the city that was beseiged, which is pretty much by definition a field command). I also think the distinction is artificial; OP is introducing a new constraint on the solution. So long as the leader is recognized as part of the command hierarchy does it make a difference if they were in the field?
