Complex sentence: The crisis of 1867 almost resulted in war between France and Prussia over the status of Luxembourg, which had become free of German control when the German Confederation was abolished at the end of the Seven Weeks War in 1866.
Split into simpler sentences: The crisis of 1867 almost resulted in war between France and Prussia over the status of Luxembourg. It involved competition between France and Prussia over control of Luxembourg, which had become free of German control when the German Confederation was abolished at the end of the Seven Weeks War in 1866.