Sentence:  But he lost the whole of his first <WSD>cohort</WSD> and the centurion of the first line, a man of high rank in his own class, Asinius Dento, and the other centurions of the same <WSD>cohort</WSD>, as well as a military tribune, Sext. Lucilius, son of T. Gavius Caepio, a man of wealth, and high position. 
Meaning of the word marked with <WSD> tags:  Any division of a Roman legion, normally of about 500 men.