The World Set Free

Wells, H. G. The World Set Free. 1913 (composition, serial publication as A Prophetic Trilogy), 1914 (book publication). UK/USA: Macmillan & Co./E. P. Dutton, 1914.

See for early reference to atomic weapons.

From the Wikipedia article: "Scientists of the time were well aware that the slow natural radioactive decay of elements like radium continues for thousands of years, and that while the rate of energy release is negligible, the total amount released is huge. Wells used this as the basis for his story. In his fiction,"

The problem which was already being mooted by such scientific men as Ramsay, Rutherford, and Soddy, in the very beginning of the twentieth century, the problem of inducing radio-activity in the heavier elements and so tapping the internal energy of atoms, was solved by a wonderful combination of induction, intuition, and luck by Holsten so soon as the year 1933. (Ch. 1, ¶1, p. 30, 1914 1st edition)[1]

Discussed in E. F. Clarke's Voices Prophesying War ch. 3, "Science and Wars-to-Come," 1880-1914, pp. 81-82, 89-90; ch. 5, "From the Somme and Verdun to Hiroshima and Nagasaki," pp. 156-57.

A quarter of a century before [Albert] Einstein wrote his letter to warn President [Franklin] Roosevelt that discoveries of the nuclear physicists had made possible the development of 'extremely powerful bombs of a new type', Wells had already given the term 'atomic bomb' to the English language'" (p. 90; see also p. 156). 

Two things make it [The World Set Free] stand out: his argument that 'because of the development of scientific knowledge, separate sovereign states and separate sovereign empires are no longer possible in the world. (p, 89)

Note also atomic warfare in "The Airlords of Han" (1929), and, quite differently, Frederick Soddy's Interpretation of Radium "Being the Substance of Six Free Popular Lectures delivered at the University of Glasgow. By Frederick Soddy. Pp. xviii+256. (London: John Murray, 1909.)"[2] Wells's acknowledgment: "To Frederick Soddy's Interpretation of Radium this story which owes long passages to his eleventh chapter acknowledges and inscribes itself" (quoted Richard Sclove, "From Alchemy to Atomic War: Frederick Soddy's 'Technology Assessment' of Atomic Energy, 1900-1915" [Science, Technology, & Human Values 14.2 (Spring 1989): 177]).[3] Better facsimile of Wells's thanks can be found, as of May 2023, here.[4]

RDE, finishing, 13Dec20, 21Dec20; 10May23, 13May23