I'd say a few church councils in the 13th and early 14th centuries like Lateran IV (1215), Lyon II (1274) and Vienne (1311) were probably the most widely known about their existence, since their canons (decrees) include the collection of subsidiary for the Holy Land (what we sometimes call "crusading tax") from wide circles of the people as well as the call for the further crusading.
The following citation, telling how Icelandic church knew about the request of the subsidiary, as decreed in the Ecumenical Council of Lyon II in 1274, in the year after the council , is taken from the Saga of Bishop Árni Þorláksson of Skálholt, in southern Iceland (d. 1298):
"In this summer [1275], Bishop Jörundr of Hólar came back to Iceland, and the above-mentioned decree of the ecumenical council [of Lyon II, the original text uses in Latin: statutum concilii generalis] also arrived. When Bishop Árni took a glance at the letters of the Pope and Archbishop Jón [Raude of Trondheim, Norway (d. 1282)], he went out for visiting across all the island, convened meetings on this issue, and preached to the people to take a cross to the journey to the Holy Land. He also remitted their sin as the Pope granted to those who [would] go to Jerusalem in person and paying by themselves for freeing the Holy Land that son of the God himself had redeemed with his blood, so that their sin should fully be acquitted......
When they heard of Bishop Árni's preach, many people took a cross as mentioned above, and some of them even promised donation. Bishop Arni also issued the document with his seal to all the people that took a cross after the papal call [for the Crusade], to testify the authenticity of their good will.
Concerning the payment of the [crusading] tithe from the church property, Bishop Árni instructed as following:
- Those who earned more than six marks in the burned silver should pay this subsidiary for freeing the Holy Land in full.
He also let the priest read/ sing the papal instruction (officium) [on this issue] once a week, and also them pray against this state of war. He called the people for the donation as much as they can so that even the God pleased them. The amount of donation was considerable.....(the Saga of Bishop Árni Þorláksson (d. 1298), Chap. 33 [ÍF XVII: 50f.])"
I cannot say everyone was so willing to hear these messages from the church council or every churchmen was so competent to tell the people on the news as Bishop Árni alleged did above. Sporadic resistances against the payment of the subsidiary (when the collector took a visit in the local church) were found here and there across Europe (Cf. Petersen 2000). Nevertheless, many peoples in Latin West had already heard the papal and council's request for the crusading tax.
Even Norse Greenlandic colonies [that also belonged to the same Norwegian archbishopric of Trondheim/ Nidaros as Iceland] were known to have paid these subsidiaries at least twice - in form of walrus tusk and seal skin ropes (Arneborg 2000: 315), so the basic instructions from the Pope as well as the council must also have reached to the north-westernmost fringe of medieval Latin Christendom, and its inhabitants, Norse Greenlanders, agreed to pay it.
In addition to the news of the Holy Land and the church council, scribes of the 13th and 14th century Icelandic annals also in fact record the obituary of not a small numbers of rulers of major kingdoms in Western Europe [England, France, Germany plus Scandinavian ones - their overlords] as well as the Pope, though I'm not sure to which extent this kind of news was shared in the local society.
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