They did lose an occasional battle, although certainly not very many. I immediately thought of the Battle of Brunanburgh, after reading your title. When I talk a course in Anglo-Saxon poetry, way back when, I memorized the opening:
Her æþelstan cyning, eorla dryhten,
beorna beahgifa, and his broþor eac,
Eadmund æþeling, ealdorlangne tir
geslogon æt sæcce sweorda ecgum
ymbe Brunanburh. Bordweal clufan,
heowan heaþolinde hamora lafan. . . .
That's easy for you to say