The answer to this can be found in Chapter 13. I cannot give the exact page number at this point because I am using the Kindle version of the book. The answer is found in a paragraph that beings “When societies do adopt a new technology…”
Diamond argues that there are four ways (he calls them “contexts”) in which an invention can spread from the society that invented it to another society. Let us look at these four.
First, the adoption may occur through peaceful trade. Diamond notes that the Japanese did not invent transistors. Instead, they got them from the United States (which had invented the transistor) by buying them.
Second, technologies may spread through espionage. In other words, people from one society might steal technological secrets from another society. Diamond provides the example of silkworms. One might also think of how the Soviet Union obtained the atomic bomb.
Third, technologies may spread through emigration. People from the society that invented the technology might move to another society. They take the technology with them, allowing their new home to have it.
Finally, war can spread technology. Diamond gives the example of how the making of paper spread from China to Muslim countries when Muslims captured Chinese papermakers in a battle.
These are the four methods of adoption that Diamond identifies.