In this Nuclear Notebook, the authors write about nonstrategic nuclear weapons—starting with the difficulty of finding a universal definition for them. Although the United States and Russia have reduced their nonstrategic stockpiles, significant inventories remain. And other nuclear weapons states appear to have nonstrategic nuclear weapons as well. Today, at least five of the world’s nine nuclear weapons states have, or are developing, what appears to meet the definition of a nonstrategic nuclear weapon: Russia, the United States, France, Pakistan, and China. The authors present information on the weapons at each of these arsenals.