28 May 1512,
Fernando II.ak from Castile wrote to the Elder Relatives of Araba, Bizkaia and Gipuzkoa from Burgos, asking for his help in the war he was going to wage against the kingdom of Navarra. The kings of Navarra, faced with this immediate intervention of the Castilian people, intensified their diplomatic efforts in search of solutions.
Source:
Joseba Asiron and Martín Altzueta, 50 key dates of the conquest of Navarra (1512-1525). (Txalaparta).