Complex sentence: Spanish troops had plundered small villages nearby on the Betuwe and even across the Rhine but this was mistaken by the Dutch and English as a feint by Parma as a possible attack on Arnhem so as a result the garrison there was reinforced.
Split into simpler sentences: Spanish troops had plundered small villages nearby on the Betuwe and across the Rhine. This was mistaken by the Dutch and English however as a feint by Parma; a possible attack on Arnhem, so as a result the garrison there was reinforced.