The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
The fundamental rule of warfare that Benjamin Franklin talks about is the following. "There is no such thing as a good war or bad peace."
That is why Benjamin Franklin -a founding father of the United States- considered that war was the most expensive way to get what a country wanted, which was territory or impose the country's ideology into another country to be invaded. Although he personally had no fear to wage war, he thought that there were other ways to accomplish things, better and less expensive than wars.