Complex sentence: In order to achieve this goal, he attended the Congress of Aix-la-Chapelle in 1818, where he was informed in confidence of an Allied pledge to interfere internally in France if a revival of revolutionary trouble was to occur.
Split into simpler sentences: In order to achieve this goal, he attended the Congress of Aix-la-Chapelle in 1818. There he was informed in confidence of an Allied pledge to interfere internally in France if a revival of revolutionary trouble was to occur.