Complex sentence: The Americans planned and tried to demolish the entire area using there artillery such as 12-pound shell guns and a massive 5-and-a-half inch motras which can technically cause horrific damage to walls and earthworks.
Split into simpler sentences: The Americans planned and tried to demolish the entire area using their artillery. This included 12-pound shell guns and a massive 5-and-a-half inch motras which could technically cause horrific damage to walls and earthworks.