Why did Pope Nicholas V disband mercenary armies in the Papal States?

Pope Nicholas V disbanded mercenary armies in the Papal States as part of his broader strategy to restore peace and stability to the region through more reliable and controlled means. Rather than relying on hired professional soldiers—who were often expensive, prone to mutiny, and capable of betraying their patrons—he chose to secure his authority by entrusting strategically located castles to carefully chosen governors.1

This approach was consistent with his stated aim to work for political and ecclesiastical peace "without using arms other than those which Christ has given me for my defence, that is to say, His Cross". By replacing volatile mercenary forces with a network of loyal, fortified positions, he sought to maintain order and preserve the status quo within his territories more effectively than the unreliable "free companies" that dominated the turbulent Renaissance era.123