Umezu later explained his decision as such: "If bacteriological warfare is conducted, it will grow from the dimension of war between Japan and America to an endless battle of humanity against bacteria.
Umezu kemudian menjelaskan keputusannya sebagai berikut, "Jika perang bakteriologis dilakukan, dari dimensi perang antara Jepang dan Amerika akan tumbuh pertempuran tak berujung antara umat manusia melawan bakteri.