Narrowing a Research Question

In practice

Narrow in order. First, start with a broad topic, such as weapons in the Second World War. Second, limit it by place, time, group or aspect: the defense of London during the Blitz. Third, limit it further to one subject within that: anti-aircraft guns. Fourth, ask how, why or what about that subject: what changes made anti-aircraft guns more effective as the Blitz went on? Fifth, check the question: can sources answer it, can it be covered in the assigned length, and does it invite analysis rather than a list of facts?