In this episode which brings elements of Larry Niven's Known Space universe into the Star Trek universe, there is mention of four wars having taken place in the mid-to-late 21st century between the feline Kzinti and humankind apparently sometime after first contact with the Vulcans. From what else is known of Trek history of this period, it seems almost impossible for four wars to have occured.
I have a theory that because Earth is not yet united that four wars can be fought in a very short amount of time if they are being fought between different nations or coalitions and the Kzinti. In fact, some of these wars may be occuring simultaneously. What do you think?