Fourth-Level Narrowing

Look at your terminology above: “critical in various battles.” Do you think you’ll be able to do a paper on the role of anti-aircraft guns in all battles of WWII? No, you won’t. So the next logical step is to look at encyclopedias and websites to determine what were some of the major battles of WWII where the use of anti-aircraft guns were critical.

You remember hearing something about “the Blitz” of London, so you look that up and decide to focus on the role of anti-aircraft guns in defending London from German planes.