Complex sentence: As time went on, the individual drummers and fife players in each company would be organised at battalion level, they retained their role in each company in battle, but would form one body of men at the head of a battalion on the march.
Split into simpler sentences: As time went on, the individual drummers and fife players in each company would be organised at battalion level. They retained their role in each company in battle, but would form one body of men at the head of a battalion on the march.