"Scholars have long debated the existence of the “nuclear taboo.” Do states refrain from using nukes because of impracticality, or do they view nuclear weapons as fundamentally immoral? The Korean War provided an important test case, because the United States had nukes, while North Korea and China did not. Moreover, few American policymakers believed that the Soviets would use any of their few primitive devices on behalf of Pyongyang or Beijing. The United States did not shy away from using strategic weapons (B-29s) for tactical purpose against North Korea; what message would the use of the Bomb have sent? We know that Truman worried about the optics of using the weapon against two (or possibly three, depending on targeting decisions) different Asian countries. We also know that U.S. allies in Europe were very nervous about the prospect of having to politically defend the use of atomic weapons against China. While it’s possible to list these reservations under either “morality” or “practicality,” it’s also quite likely that using atomic weapons against China would have lowered the psychological and bureaucratic thresholds for using them in future conflicts against non-nuclear powers."