The acquisition of this map benefited from Yang, former deputy head of the training regiment of the 22nd Corps of the Kuomintang, who had close ties with the underground party in China. Yang found it. Zhang Youxi is a staff officer in garrison headquarters, Xiamen. He is good at painting and has close ties with underground parties. Two people work closely together to draw pictures and Yang explains them. In this way, a map of Xiamen's defensive forces and firepower distribution was quickly drawn.