How would an earlier and more widespread cavity magnetron change the Second World War?
Short answerEarlier compact radar would most benefit states able to mass-produce and display it effectively, especially Britain and later the United States, with major consequences for air warning, ships, aircraft, and submarine detection.
NotesThe decisive advantage lies in the ability to manufacture complete systems and present contacts usefully to operators. Earlier compact radar could improve ship and aircraft search, expose submarines and periscopes, and amplify Britain's prewar radar infrastructure before American mass production expands the advantage.