In reality, the plot had been "uncovered" when a prisoner (being held for unrelated crimes) confessed to it and implicated members of various noble houses.

Historian Leopold von Ranke gives an account of a 1639 visit to Rome by Odoardo Farnese, Duke of Parma and Piacenza.

But the Duke refused to pay due deference to the Pope's other nephew; the newly appointed Prefect of Rome, Taddeo Barberini.

[2] Pope Urban VIII responded to the requests of Duke Odoardo's creditors by sending his nephew Antonio, Fabrizio Savelli and Marquis Luigi Mattei to occupy the city of Castro.

[4] Spada later published a manifesto detailing his version of events which, according to contemporary John Bargrave, many accepted to be the truth.

Mercenaries and regular troops filled the streets and Antonio Barberini was forced to institute special measures to maintain authority over the city.

[6] The pope's forces were met by a contingent of 40 troops guarding a bridge leading to the town; a short burst of cannon-fire resulting in a single death was enough to prompt capitulation.

The army was split into three and the Pope's nephew, Taddeo Barberini, replaced Savelli as Generalissimo, arriving with one contingent in the papal city of Ferrara on 5 January 1642.

But Odoardo faltered and the Pope was able to fortify Rome and raise a new army - this time 30,000 troops; enough to drive the Duke back to his own territory.

[2] Exasperated, the Pope increased taxes and raised additional forces and the war continued with Cardinal Antonio Barberini (Taddeo's brother) finding success against the Venetians and Modenese.

But Papal forces suffered significant defeats in the area around Lake Trasimeno at the hands of the Tuscans (the Battle of Mongiovino).

This peace settlement concluded the First War of Castro and was widely considered a disgrace to the papacy, which was unable to impose its will through use of military force.

In total, the first war is estimated to have cost the papacy 12 million scudi and special taxes were levied against the residents of Rome to refill church coffers.

When the bishop was killed en route to Castro, near Monterosi, Pope Innocent X accused Duke Ranuccio and his supporters of murdering him.