During Odoardo's reign the declining Duchy had been involved in the Wars of Castro, over the above-mentioned duchy of Castro, which was a Farnese fief in the Papal States, north of Rome, which the powerful Pope Urban VIII's family, the Barberini, was eager to acquire.
They found the excuse when Odoardo was unable to repay his creditors, from whom he had incurred debts.
Urban responded to the creditors' plea for help and had Castro occupied.
However, the first war ended with Papal defeat.

Ranuccio refused to repay the debts incurred by his father, despite the latter having a signed a peace treaty agreeing to do so.
He also refused to recognise the new bishop of Castro, appointed by Urban's successor, Innocent X. In 1649, the new bishop, Cardinal Cristoforo Giarda, was murdered on his way to Castro.
Innocent accused Ranuccio of the murder and in retaliation, forces loyal to the Pope besieged Castro, and then razed it to the ground.
In August of that same year the Parmense troops had been crushed not far from Bologna, and Ranuccio remained with no means to gain back his fief, despite his attempts to buy it back with money.

In 1672 he bought the principate of Bardi and Compiano from Gianandrea Doria Landi, giving the Duchy its final shape.

In the last days of his reign, the Duchy suffered heavily from the presence of Imperial troops, who were fighting in the dispute between Victor Amadeus II of Savoy and France.
During Odoardo's reign the declining Duchy had been involved in the Wars of Castro, over the above-mentioned duchy of Castro, which was a Farnese fief in the Papal States, north of Rome, which the powerful Pope Urban VIII's family, the Barberini, was eager to acquire. They found the excuse when Odoardo was unable to repay his creditors, from whom he had incurred debts. Urban responded to the creditors' plea for help and had Castro occupied. However, the first war ended with Papal defeat.
Ranuccio refused to repay the debts incurred by his father, despite the latter having a signed a peace treaty agreeing to do so. He also refused to recognise the new bishop of Castro, appointed by Urban's successor, Innocent X. In 1649, the new bishop, Cardinal Cristoforo Giarda, was murdered on his way to Castro. Innocent accused Ranuccio of the murder and in retaliation, forces loyal to the Pope besieged Castro, and then razed it to the ground. In August of that same year the Parmense troops had been crushed not far from Bologna, and Ranuccio remained with no means to gain back his fief, despite his attempts to buy it back with money.
In 1672 he bought the principate of Bardi and Compiano from Gianandrea Doria Landi, giving the Duchy its final shape.
In the last days of his reign, the Duchy suffered heavily from the presence of Imperial troops, who were fighting in the dispute between Victor Amadeus II of Savoy and France.
Ranuccio II Farnese, Duke of Parma