Research Papers / The relationship between samurai and ninja in feudal Japan, Essay Topic Help (IB) [2]

Okay, so:

Currently, my selected topic is the relationship between samurai and ninja in feudal Japan. This encompasses a large time frame, about 600-800 years depending on where you place your cut off date. It just hit me that this is rather broad. Should I try and narrow down my topic? And if so, to what? Thanks for your help