Complex sentence: Napoleon was interested in having Spain as an ally against England, in the summer of 1800, he sent his brother Lucien to the Spanish court with the proposal that would result in the Treaty of Aranjuez.
Split into simpler sentences: Napoleon was interested in having Spain as an ally against England. In the summer of 1800, he sent his brother Lucien to the Spanish court with the proposal that would result in the Treaty of Aranjuez.