During the same period, he also began to work on the history the Moluccas, especially on the Ambonese, whom de Graaf thought the Dutch owed a "duty of gratitude" for helping "enrich" the Dutch and spreading their authority around Indonesia.
Selama periode yang sama, dia juga menyusun tentang sejarah Maluku, khususnya di Ambon, di antaranya de Graaf pikir belanda berutang "tugas syukur" untuk membantu "memanjakan" Belanda dan menyebarkan kekuasaan mereka di seluruh Indonesia.