Toshihiro Higuchi’s Political Fallout: Nuclear Weapons Testing and the Making of a Global Environmental Crisis has already been the subject of an H-Environment Roundtable Review (Vol. 11, no. 5, 2021). It is a testament to the interdisciplinary character of Higuchi’s book that it is now the subject of an H-Diplo Roundtable Review. The Partial Test Ban Treaty (PTBT) of 1963, which prohibited nuclear weapon tests in the atmosphere, in outer space, and under water, has been widely discussed in studies of the US-Soviet nuclear rivalry and nuclear arms control. Higuchi’s book presents the treaty in a wholly new light, as a response to the global environmental crisis created by nuclear weapon tests and the radioactive fallout those tests produced.