According to his nephew, during this period, he wrote his first book (perhaps in winter quarters when the more spare time was available), a work on the use of missiles on horseback, De jaculatione equestri.
I henhold til hans nevø, var det i løbet af denne tid, at han skrev sin første bog (måske i løbet af vinteren da ledig tid var mere tilgængelig), et arbejde om kavaleriets brug af kasteskyts, De jaculatione equestri.