Mencius - Book 2, Part 2, Chapter 1B

'In accordance with these principles it is said, "A people is bounded in, not by the limits of dykes and borders; a State is secured, not by the strengths of mountains and rivers; the kingdom is overawed, not by the sharpness and strength of arms." He who finds the proper course has many to assist him. He who loses the proper course has few to assist him. When this, the being assisted by few, reaches its extreme point, his own relations revolt from the prince. When the being assisted by many reaches its highest point, the whole kingdom becomes obedient to the prince.

'When one to whom the whole kingdom is prepared to be obedient, attacks those from whom their own relations revolt, what must be the result? Therefore, the true ruler will prefer not to fight; but if he do fight, he must overcome.'
~ James Legge translation via nothingistic.org ~

Go here to read the introductory post to this serialized version of the Works of Mencius.