What does "knowledge is power" mean from a commonsensical point of view?

A more drastic proverb would be "a pen is mightier than the sword". However, I don't think that knowledge alone confers power to someone. Just consider a leading theoretical physicist lost in the jungle. It can be easily seen that the knowledge must, first, be relevent to the person's situation.

Now let's test: "Relevent knowledge is power." True? So suppose there is a war between two nations, and a strategist knows just the right strategy to deal with either country. However, neither country is willing to employ him. Is his relevent knowledge powerful? I doubt so.

Now let's retreat further and test:"Relevent knowledge confers power when used." I think this starts to make more sense. I'm not sure if this is acceptable, but when one say something is knowledge, it must somewhat hold true for an extended period of time. Thus, when one has knowledge, one would be able predict future events in the relevent field given enough relevent information, and when he has the power to change the input, he can manipulate the input to achieve the desired output. However, if he has no power to change the input, even with extensive knowledge, he cannot change the output.

Thus, I propose that "Relevent knowledge confers additional power when one's available power allows him to use that knowledge."