Complex sentence: With the Pope as a substitute father, Mortara trained for the priesthood in Rome until the Kingdom of Italy captured the city in 1870, ending the Papal States; leaving the country, he was ordained in France at the age of 21 three years later.
Split into simpler sentences: With the Pope as a substitute father, Mortara trained for the priesthood in Rome until the Kingdom of Italy captured the city in 1870, ending the Papal States. Leaving the country, he was ordained in France at the age of 21 three years later.