张择端的名画《清明上河图》,再现了北宋都城开封的水陆交通及人们的日常生活。看似包罗万象的《清明上河图》上,却缺少了两种市井常见动物——马和羊。这是为什么呢?原来,马和羊牵扯到北宋的军事机密。北宋是典型的民富国穷,宋太祖赵匡胤一开国,就奠定了重文轻武的基本国策。北方虎视眈眈的游牧民 Zhang Zeduan’s famous painting “Riverside Picture of Qingming,” reproduced the water and land transportation and people’s daily lives in the capital of the Northern Song Dynasty in Kaifeng. Seemingly all-enviable “Qingming Riverside”, but the lack of two common market animals - horses and sheep. Why is this? It turned out that the horse and sheep involved in the Northern Song military secrets. The Northern Song Dynasty is typical of the rich and poor countries, the Song Taizu Zhao Kuangyin, the founding of a country, it laid the basic national policy of heavy text light weapons. Nomads flocked to the north