Complex sentence: The main concentration of fire was on the right (east) bank of the Meuse, and 26 superheavy long-range guns, up to, fired on the forts and the city of Verdun; a rumble could be heard away.
Split into simpler sentences: The main concentration of fire was on the right (east) bank of the Meuse river. Twenty-six super-heavy, long-range guns, up to, fired on the forts and the city of Verdun; a rumble could be heard away.