The idea of the Defensive War was conceived by Jesuit father Luis de Valdivia who sought to diminish hostilities, establish a clear frontier and increase missionary work among the Mapuches.
[1][2] The Defensive War became Spain’s official policy in 1612 when King Philip III decreed it after reading a letter from Valdivia.
[4] To carry out his missionary work Luis de Valdivia recruited eight Jesuits and two coadjutors in Spain to travel to Chile.
[4] The Mapuche toqui Anganamón killed three Jesuit missionaries on December 14, 1612 after he learned the Spanish were protecting his two fugitive wives and two of his daughters.
[5] De Tesillo claim the Defensive War gave the Mapuche a much needed respite to replenish their forces that should have been denied.