<論説>明初の対モンゴル軍事政策とその帰結

Abstract

モンゴル帝国は中国を軍事征服したが、明はモンゴル勢力を軍事的に屈服させることはできなかった。これは専ら軍事的条件の相違による。中国から草原地帯に侵攻しても占領地を経営することができないため、段階的に領土を広げていくことができず、軍事基地を維持することさえ困難であった。そのため、明側から攻撃をしかける場合、補給上の制約を受け、可能な軍事行動の範囲は著しく限定された。兵力において優勢であっても効果的に打撃を与えられず、逆に殲滅される危険性が高く、敵を追い詰めることは事実上不可能であった。しかも攻勢に出た場合の財政負担は甚大なものとなった。永楽帝の親征は、この制約下で最大限の努力をしたものと言えるが、実質的成果は僅かであり、最終的には財政的限界によって行き詰る。こうして明からモンゴル側への攻勢は無益と証明され、明は防衛に徹した軍事体制を維持するため、国内制度を整備することを余儀なくされた。

Although the Mongol empire had been able to conquer China, the Ming dynasty could not subdue the Mongols by military means. This fact was chiefly due to the differences in military conditions. Because it was extremely difficult for the Chinese to manage occupied areas in the steppes, the Ming could not expand its territory into Mongolia, and found it difficult even to maintain military bases there. For that reason, when Ming forces took the offensive, her troops always had to march off to distant enemy targets. On such occasions, the Ming troops had to be supplied over great distances from their own territory because little food could be obtained in the enemy's land. These conditions restricted the military operations of the Ming. Her armies had to defeat the enemy in a short period and turn back immediately before their provisions would run out. When they faded to capture the enemy, they had no choice but to retreat in vain to their own territory. Even if they fought and won a battle, they could not pursue the defeated enemy for any great distance. Accordingly, it was practically impossible for them to press the enemy. Moreover, if they went too deep into enemy territory, they could not expect to be sent reinforcements and faced the danger of annihilation. Li Wenzhong 李文忠 who gained a victory in 1372 narrowly achieved his objective, but Qiu Fu 丘福 suffered a crushing defeat in 1409, although both men had carried out similar plans of operation. The Yongle Emperor 永楽帝 made expeditions into Mongolia five times. His tactics did not differ much from those of Li Wenzhong or Qiu Fu. But he and his ministers devised a plan that would guarantee victory if their army could capture the enemy. They decided to send an overwhelmingly large army and to secure sufficient supplies, and took all possible measures to pat the plan into practice. The Yongle Emperor succeeded in doing a certain amount of damage to his enemies on the first and second expeditions, although unable to deal a decisive blow. However, expenditures for the war threw his government into financial trouble, and labor service imposed on the people was so heavy that it severely impoverished the countryside. His last expedition ended in stalemate mainly due to a lack of war supplies. As the Mongolian leaders who had once yielded to him regained their strength, the Yongle Emperor's attempts turned out to have been fruitless. Thus it was proved that a military campaign from Ming territory into Mongolia was useless. After the Yongle Emperor's death, his successors concentrated their strategy on defense. The military establishments on the northern frontier which the Hongwu Emperor 洪武帝 had built up were maintained and further developed. When the Ming troops stood on the defensive, they were never at a military disadvantage and their strong fortresses kept the enemy at bay. Though Mongols could not be conquered by the Ming even when Mongol peoples were in disunity and a weakened state, they could not conquer the Ming even after they became unified and powerful. From there on, the military strength of the Ming and that of Mongols remained in balance on the whole, and this state continued until the Qing dynasty conquered both China and Mongolia in the 17th century. Throughout the Ming period, the emperors and their governments had to maintain their defenses on the northern border at great cost. Particularly, after it became apparent that such a defense framework would be permanent, they were obliged to devise methods to reduce defense costs and put imperial finances on aim basis. These methods occupied a large part of administration of the Ming. Consequently, the military balance between the Ming and Mongols began to influence all aspects of Ming policy.