Sun Tzu teaches two key ways to win a battle, that is, a meeting of opponents, of two evenly matched opponents. The first is preparing a surprise beforehand. There is always a risk in this because battle is unpredictable, but the idea is that you will be better prepared than your opponent. If it works, the confusion of surprise creates an opening that you can use. If you aren't prepared to risk a surprise, you have to wait for your opponent to make a mistake and take advantage of it.