Complex sentence: The game adds a new strategy mode called "empire mode" which is based on the "Romance of the Three Kingdoms" series, however the gameplay during attacking or defending against opposite forces is exactly the same as the original "Dynasty Warriors 4".
Split into simpler sentences: The game adds a new strategy mode called'Empire Mode' which is based off of the "Romance of the Three Kingdoms" series. However, the gameplay during attacking or defending against opposing forces is exactly the same as the original "Dynasty Warriors 4".