His prominence in medieval history is due partly to the share he took in the Western Schism, but chiefly to his involving himself in the long-standing disputes between the Teutonic Knights of Prussia on one side and the allied Kingdom of Poland and Grand Duchy of Lithuania on the other.
Falkenberg wrote a book, Liber de doctrina, published 1416,[2] opposing Polish scholar Paulus Vladimiri.
Liber de doctrina argued that the King of Poland and his adherents were idolators, and unbelievers; that the opposition against them was noble and praiseworthy.
"[1] Stanislaus F. Belch in his work Paulus Vladimiri and his Doctrine concerning International Law and Politics wrote that he was the first writer to formulate justification of genocide.
In this work, moreover, he denied the bishops the right to declare his book or any part of it heretical, claiming that in matters of faith the pope and general councils alone are infallible.