Complex sentence: The confederate army was raised against the members of the "Sonderbund", composed of soldiers of all the other states except Neuchâtel and Appenzell Innerrhoden, which had stayed neutral.
Split into simpler sentences: The confederate army was raised against the members of the Sonderbund. The army was composed of soldiers of all the other states except Neuchâtel and Appenzell Innerrhoden which had stayed neutral.