Charles Oman 
The Dark Ages [EPUB ebook] 

Sir Charles William Chadwick Oman KBE (1860-1946) was a British military historian.
His reconstructions of medieval battles from the fragmentary and distorted accounts left by chroniclers were pioneering.
Occasionally his interpretations have been challenged, especially his widely copied thesis that British troops defeated their Napoleonic opponents by firepower alone. Paddy Griffith, among modern historians, claims that the British infantry’s discipline and willingness to attack were equally important.