Chu-ke Liang had studied the weather.He knew that the southeast wind would begin to blow in a couple of days,but he convinced Chou Yu that he had magic powers and that he could summon wind and rain.He suggested to Chou Yu,"Why don't you build an altar where I can practise my magic and borrow the southeast wind for you for three days and nights?"Since Chou Yu had competely recovered after unburdening his heart to Chu-ke Liang.He asked his soldiers to build an altar on Nanp'ing hill and invited Chu-ke Liang to practise his magic there.