Decio Azzolino (11 April 1623 – 8 June 1689) was an ItalianCatholicCardinal,code-breaker, investigator and leader of theSquadrone Volante.
Azzolino was born atFermo, the son of Pompeo Azzolino and GiuliaRuffo. He was the great-nephew of Cardinal Decio Azzolino, the elder, and is thus often referred to as Cardinal Decio Azzolino, the younger.
He received doctorates in philosophy, law and theology from the University of Fermo.[1] On 18 January 1642Pope Urban VIII named BishopGiovanni Giacomo Panciroli nuncio extraordinary to Spain. Azzolino followed Panciroli to Madrid, and in 1644 whenPope Innocent X appointed Panciroli as secretary of state, he began assisting him in the secretariat. When Panciroli died in September 1651, Azzolino managed the secretariat until the return of BishopFabio Chigi from Germany. Chigi was named secretary of state in December.[2]

Azzolino was a skilled cryptographer, responsible for crackingciphers used in correspondence. He was also an able investigator. When theKingdom of Naples was made aware of invasion plans byHenry II, Duke of Guise, it was Azzolino who (in February 1654) concluded that the breach must have come fromCamillo Astalli, the Pope'sCardinal-Nephew. Though likely accurate, his conclusion was convenient - Astalli was a rival for power toOlimpia Maidalchini, Azzolino's own patron.[3] ContemporaryJohn Bargrave noted that there were plenty of spies within the Vatican but that none excelled at the task more than Azzolino.

Later in 1654, because of this service he rendered to the pope, Azzolino was elevated to cardinal and was madecardinal-priest of the church ofSant'Adriano al Foro (Curia Julia) in Rome.
He participated in thepapal conclave of 1655 which electedPope Alexander VII. Azzolino was the leader of the independentliberal movementSquadrone Volante, which played a role in engineering the result of the conclave in favour of an anti-nepotism candidate.[4] Azzolino's Squadrone also is thought to have engineered the election of Giulio Rospigliosi asPope Clement IX at thepapal conclave of 1667.[4] Rospigliosi, who had beencardinal secretary of state, rewarded Azzolino by immediately (on the night of his election, in fact) appointing him to the position,[3] giving further credence to the rumour.

Azzolino was appointed QueenChristina of Sweden's representative within theCatholic Church.[citation needed] It is certain he looked after her financial businesses. Some have speculated that he and Christina were in love with one another. Bargrave, again, suggested that Azzolino was sent toRomania[citation needed] by Pope Alexander in order to avoid public perception that a relationship was ongoing.
In July 1659, she moved toTrastevere to live inPalazzo Riario, on top of theJaniculus, designed byBramante. It was Cardinal Azzolino who signed the contract as well as provided her with new servants to replaceFrancesco Maria Santinelli, who had beenMonaldeschi's executioner. Azzolino ensured that she was reconciled with the pope and that the latter granted her a pension.
Christina wrote him many letters during her travels. On 26 January 1667, Christina wrote (in French) that she never would offend God or give Azzolino reason to take offence, but this "does not prevent me from loving you until death, and since piety relieves you from being my lover, then I relieve you from being my servant, for I shall live and die as your slave". Maintainingcelibacy, his replies were more reserved.
In 1675, he suggested Christina to appointRomolo Spezioli, also from Fermo, like Cesare Machiati, as her physician.[5] Azzolino also introduced her toMiguel Molinos. In her basement there was a laboratory, where she,Giuseppe Francesco Borri and Azzolino experimented withalchemy. Cardinal Azzolino stayed at her side until she died on 19 April 1689.
Azzolino burnt most of their correspondence; about 80 letters have survived. Some details were written in a code that was decrypted byCarl Bildt in Rome around 1900.[6] Azzolino inherited herimportant art collection, includingCorreggio'sDanaë and two versions ofTitian'sVenus and Adonis (probably the "Lausanne" and Getty versions). Azzolino died a few weeks later and is buried in theoratorium of the Church ofSanta Maria in Vallicella. His nephew Pompeo Azzolino was his sole heir, and he rapidly sold off Christina's art collections, much of which later formed the core of theOrleans Collection.