Often misattributed to Sun Tzu, the above quote was actually first uttered by Chris Bradford: an English author and black belt martial artist, best known for his children's fictional series, Young Samurai.
The first Young Samurai book, The Way of the Warrior, was published by Puffin Books in 2008. Disney bought the rights in the same year and published in early 2009. Seven further books followed, with a ninth - The Return of the Warrior - being published for the series' tenth anniversary in 2018.