Complex sentence: The War of the Reform (1858-61) ended with the defeat of conservatives, but the liberal government of Benito Juárez defaulted on foreign loans in 1861, opening the door to foreign intervention supported by Mexican conservatives.
Split into simpler sentences: The War of the Reform (1858-61) ended with the defeat of conservatives. Then liberal government of Benito Juárez defaulted on foreign loans in 1861, opening the door to foreign intervention supported by Mexican conservatives.