承唐授宋的五代，向來被視為大唐帝國之殘局，其實也是歷史大轉捩時期的起點，經過五代逾半世紀的紊亂與重整，催生了文化璀璨的宋朝。在北宋建國167年之後，再度因為北方遊牧民族之壓迫而偏安江南。國防上，導致外族入侵宋朝的原因，最常見的指責就是石敬瑭割燕雲之地與契丹，然則，失去燕山之險的中原王朝，從此不再能夠反制契丹的入侵了嗎？
唐末的河東軍兩度東出佔領幽州，主導河北諸鎮，繼而建後唐、滅後梁；五代後晉的河東軍數度不支援河北戰場，導致中原遭契丹滅國；後漢則由太原南下接收契丹留下的中原殘局。由確保首都安全的角度，太原位置與幽州互為表裏而成為中原肩背，北宋無論建都於開封或洛陽，都以嚴控太原，置重兵於河北、河東為必要之布置。不過，北宋承襲後周集中強大中央禁軍於汴洛地區的經驗，又有北漢據太原頑抗的教訓，更不至於再度將重兵布署在河東了。宋朝了解汴京地理形勢不佳，企圖以「兵險」取代「形勢」，其決策顯然是根據短淺的五代經驗，且有理則上的扞格。
本文嘗試將唐末的中原區分為四大區塊，經由爬梳五代政權的更迭過程，探討此間對地理形勢的運用情形。
Five Dynasties has long been regarded as the remnants of the Tang Empire, in fact, it is also the starting point of the historical transition period. After nearly a century of disorder and restructuring, the Five Dynasties gave birth to the culture of the Song Dynasty. 167 years after the founding, once again, Song Dynasty moved to the south of the Yangtze River because of the northern nomadic people invasion. In the national defense, the reason of causing nomadic invasion Song Dynasty, most common accusation was that ceded Youzhou(幽州) to the Khitan by Shi Jingtang(石敬瑭). However, that loss of Yanshan(燕山) border station, Would the Song Dynasty no longer be able to resist the Khitan invasion?
The Hedong military(河東軍) occupied the Youzhou twice in the end of Tang Dynasty, leading the Hebei(河北) warlords defeated the HouLiang(後梁) Dynasty and set up the HouTang(後唐) Dynasty. Later, HouJin(後晉) was destroyed by the Khitan that cause of The Hedong military does not support the Hebei battlefield three times. The HouHan(後漢) Dynasty established in Hedong and received the Central Plains regime which was derelict by the Khitan. So, if our point based on the protection of the security of the capital that will found Taiyuan(太原) and Youzhou position of location are complementary to each other and can be rely of the Central Plains regime. No matter the Song’s capital at Kaifeng(開封) or Luoyang(洛陽). Song Dynasty should make up a powerful troops in Hebei and Taiyuan and must be exercise strict control over them. The problem is that the Song dynasty inherited the strong central army concentrated in the Kaifeng(開封) area, as well as the BeiHan(北漢) had occupied Taiyuan recalcitrant, those unpleasant experience let the Song Dynasty did not put important military in the Hedong again. Therefore, Kaifeng flawed geography situation makes the Song Dynasty so trying to cantonment large numbers of troops to replace the geographic situation, its decision was obviously based on the short experience of the Five Dynasties.
This paper try to divide Central Plains area with four large blocks. Through the historical record of Five Dynasties regime change process and display the impact of geographical situation for Five Dynasties.
