Even though the "I" for "international" was included in the BAAS Division name, it did not seem to have many consequences until World War II.
Bernal's book, "the social function of science",3 is usually considered as the main expression of this movement. A chapter is untitled "international science". It has 4 pages of general considerations, and nearly 50 for a quick overview of science beyond United Kingdom: other European countries, fascist countries, socialist countries, India, China, and Japan…
Bernal's doctrine is clearly exposed in the first sentences: "The internationalism of science is one of its most specific characteristics. Science has been from the start international in the sense that men of scientific temper even in most primitive times were willing to learn from others in different tribes or races. (…) In later times, when natural barriers separated civilizations, or when religions or national animosities divided the civilized world into hostile camps, the scientist vied with the trader in breaking down those barriers". And further: "Internationalism in science was maintained and even increased throughout the 19th century, but the present century has marked a definite retrogression. Science, while still remaining international, has begun to suffer from the general tendency towards national exclusiveness, and the unity of the scientific world is being seriously threatened".
The economical crisis, capitalism, socialism, and the struggle against fascism… this entire context was directly, and only, international in the late 1930s. Furthermore, being universal, science was evidently international. Nobody had to bother more about what it meant exactly, and what the practical consequences were. To the point that, concluding his half page about India, Bernal wrote: "probably the best workers for Indian science to-day are not the scientists but the political agitators who are struggling towards a self-reliant and free community".