Complex sentence: France and the United Kingdom of Great Britain and Ireland had just despatched a joint military expedition to the Far East to chastise China under the Xianfeng Emperor, and the French had troops on hand with which to intervene in Annam.
Split into simpler sentences: France and the United Kingdom of Great Britain and Ireland had just despatched a joint military expedition to the Far East to chastise China under the Xianfeng Emperor. As a result, the French had troops on hand with which to intervene in Annam.