Nonsense. Justice Grier refers to it as a rebellion.
The later correspondences are in the War of the Rebellion records.
Acknowledgement of receipt of an unsolicited correspondence? And the reply from the Holy Father was? Or was there a reply at all? And what about this protection from arrest you spoke of?
Justice Grier is not the pope.
Acknowledgement of receipt of an unsolicited correspondence?
Not at all. By 1864, Cardinal Antonelli (the head of the Vatican's diplomacy) had been engaging in diplomatic activities with Mann for over a year. Mann reported reaching Rome on Nov. 11 1863 where he was recieved by Antonelli:
"On the 11th, at half past 1 p. m., I sought and promptly obtained an interview with his Eminence, the Cardinal Secretary of State, Antonelli. I at once explained to him the object of my mission to Rome and he instantly assured me that he would obtain for me an audience of the sovereign Pontiff."
Antonelli arranged for a meeting between Mann and the Pope on the 14th. Mann and Antonelli met again on the 21st. It was at this meeting that Antonelli extended diplomatic protection to Mann following the objections of the yankee government over the Vatican's reception of him earlier that week:
"He [Antonelli] took the occasion to inform me, at the commencement, that the acting representative of the United States had obtained an interview of him the day before to remonstrate against the facilities afforded by the government of the holy see to "Rebels" for entering and abiding in Rome; and that he, the cardinal, promptly replied that he intended to take such "Rebels" under his special protection, because it would be making exactions upon elevated humanity which it was incapable of conscientiously complying with, to expect them to take an oath of allegiance to a country which they bitterly detested."
Thus, by 1864, relations between Mann and the Vatican were already well established.
The 1864 letter I quoted from was one of many diplomatic exchanges between the CSA and Vatican, not an unsolicited response. In fact, it appears to be a followup response to a meeting between Antonelli and a CSA diplomat, JT Soutter, on Nov. 20, 1864. Antonelli and Soutter met at length to discuss relations between the Vatican, the north, and the south. Soutter then delivered some sort of document from the CSA congress to Antonelli, which is the subject of the letter Antonelli sent back a week or so later.
And what about this protection from arrest you spoke of?
See above. Shortly before Nov. 21st 1863 the yankees lodged a protest with the Vatican for recieving Mann. Antonelli responded by granting Mann diplomatic protection.