chapter 1 or 2 of part 2 for the nukes. the ongoing war thing I think is an asspull.
In the Reze or the Gun Devil arc, it's mentioned that there was an ongoing war between the USA and the Soviet Union. I'm not sure if it was supposed to be a Cold War, but Reze was an agent working for the Soviets with the mission of
retrieving the gun devil parts owned by the Japanese government. The gun devil parts were the equivalent of nukes in the world.
Depending on how much of the gun devil parts Yoru summoned to her, she may have caused the unintended consequence of getting rid of the only thing holding the two countries from going full-on war, and with the USA (re)inventing the nukes, most likely have taken the initiative to be the first to strike when the Soviets don't have a equivalent of nukes anymore.