He served as an assistant to Cardinal Adeodato Giovanni Piazza at the First General Conference of the Latin American Bishops in Rio de Janeiro, Brazil, in 1955.

[1] During the period following Vatican II, Casaroli gained a reputation as a highly skilled diplomat who was able to negotiate with regimes hostile to the Church.

Although he was seen as less hardline than any other close associate of John Paul, Casaroli's skillful diplomacy was seen by Wojtyła as an irreplaceable asset in the struggle against the Soviet Union.

According to John O. Koehler, the KGB and its "brother organs" in Eastern Europe were well aware of Cardinal Casaroli's real opinions and influence.

Inside the revered religious icon was a "bug", a tiny but powerful transmitter, which was monitored from outside the building by the couple's handlers from the Soviet Embassy in Rome.

Both were not discovered til 1990 during a massive probe initiated by Magistrate Rosario Priore in the aftermath of the assassination attempt on Pope John Paul II.

"[3]On 10 June 1981, on the 100th anniversary of Pierre Teilhard de Chardin's birth, L'Osservatore Romano, the official Vatican newspaper, published a letter by Casaroli that praised the "astonishing resonance of his research, as well as the brilliance of his personality and richness of his thinking."

Casaroli wrote that Teilhard had anticipated John Paul II's call to "be not afraid", embracing "culture, civilization and progress".

[5] Cardinal Casaroli was portrayed by veteran character actor Ben Gazzara in the 2005 miniseries, Pope John Paul II.