帝國之隙：唐代前期的軍政危機及其對策

本論文聚焦於唐代前期（618-755；從唐朝開國至安史之亂爆發前；武周時期（690-705）亦包含在內）所出現的各種軍事與政治危機及挑戰，以及此期間諸位唐朝皇帝及其高級官員所採取的對策與因應作為。唐高祖李淵建立了唐帝國，同時也為帝國的軍政制度奠定基礎。李淵為了解決當時所面臨的種種問題，遂從既有的當代制度以及傳統舊制中找尋其可用者，加以適當地改造後，應用於建立其帝國草創時期的軍政體制，其中以行臺、總管、使職等制度相互搭配而構成的地方軍政授權制度，係其尤其重要者。另一方面，李淵也改造西魏以來迄於北周所使用的府兵制，藉以重新整編、訓練其為數眾多但欠缺整合的大批軍隊，以強化其戰力；此外，李淵也將府兵分配部署至京師長安周遭的關中地區，建立軍區式的關中十二軍體系，以資對抗北方深具威脅性的東突厥。李淵對於新舊制度的運用與創造，充分展現其充滿權變特色的作風。唐太宗李世民滅東突厥後，便取消了十二軍之制，並改革府兵制，以節省軍事開支；然而，太宗往後卻數度發動大規模對外戰爭，導致新府兵制承受過大的負擔。唐高宗李治在位期間，周遭各民族政權崛起，唐帝國在與鄰近各政權競爭的過程中耗費許多資源，兵員也蒙受大量損失，府兵制的運作也面臨更大的壓力。高宗朝開始實施類似十二軍之制的新軍事制度，派遣許多將領擔任使職，率兵長期駐守於戰略要地作為防禦力量；而使職也因其較佳的效率，逐漸成為唐帝國最為重要的軍事與政治制度成分。武則天統治期間，其注意力主要放在鞏固自身政治權力方面，從而忽略了軍事體系方面的敗壞，過度的兵役負擔造成了嚴重的逃戶問題。直到唐玄宗李隆基時期，才漸施行政治與軍事方面的改革以應付沉痾。帝國邊境陸續建立起以節度使擔任長官的大型軍政授權區，並以專業化的士兵負責軍事防務。使職的應用也幾乎遍於帝國政務的各個方面，而執政的權力也主要集中於由諸位宰相主持的「中書門下」。雖然唐帝國的實力確實因為改革而有所提升，但玄宗對於自身軍事才能與統御臣下技巧的高度自信，卻導致他逐漸忽視了對於節度使在其轄區內之巨大權力施加制衡的必要性；任命單一將領同時擔任兩個以上的節度使職位，這種情況在玄宗朝屢次出現。結果，其中一位兼任多個節度使的大將安祿山所掀起的安史之亂，不但重擊了玄宗的過度自信，也將唐帝國的裂隙撕成了巨大的缺口。

關鍵字

唐朝；唐帝國；府兵；十二軍；軍事；政治

並列摘要

This research is focused on the cracks, which means the military and political crises and challenges, and the countermeasures taken by the Emperors and ruling class of the Tang Empire during its early period (618-755; before the An Lushan Rebellion), including the Wu Zhou Dynasty (690-705). Emperor Gaozu of Tang (Li Yuan李淵), the founder of the Tang Empire, used several existing, traditional or historical military and political institution to satisfy the needs and solve the problems toward the current situation of that time. On the one hand, Emperor Gaozu established the new local authorizing system in both military and political aspects by the institutions like zong-guan (總管), xing-tai (行臺) and official positions named with shi (使職) , which indicated some high level royal representatives; on the other hand, he applied the military system “fubing” (府兵), which was operated from the Western Wei to the Sui Dynasty, to train his numerous but mostly raw soldiers, and created a new defensive system by deploying his soldiers called fubing into the 12 military regions spreading near the capital Chang-An (長安) in the Guan-zhong (關中) area as the twelve corps (十二軍) to resist the invasion of the Eastern Turkic Khaganate. After extinguishing the Eastern Turkic Khaganate, Emperor Taizong of Tang (Li Shimin 李世民) cancelled the twelve corps and renewed the fu-bing system to reduce the military cost. However, Emperor Taizong launched several major wars toward other foreign regimes or kingships, causing his new fubing system confronting burdens it bore hardly. During the reign of Emperor Gaozong (Li Zhi李治), the surrounding foreign regimes gradually rose, and the Tang Empire expended so much resources to compete against them, losing plenty of military manpower and then devastating the fubing system much more. Emperor Gaozong began to use a new military system similar to the twelve corps, deployed many generals and soldiers resident in a lot of important areas or forts as defensive forces, and this system ran with the shi institutions, which became the most popular military and political institutions in the Tang Dynasty, for their better efficiency. While Emperor Wu Zetian (武則天) was ruling the empire, her main attention was concentrating on the stability of her political power, resulting in her neglect of the decay of the military system; the heavy burden from military service brought about common people escaping from home to avoid it. Until the reign of Emperor Xuanzong of Tang (Li Longji李隆基), reformations in both political and military systems and institutions were gradually put into practice to fill the cracks of the empire. Several large military and political regions each commanded by a jiedushi (節度使), who was the highest general and administrative official in his commanding region, were established across the border of the empire. The military responsibilities were held by professional soldiers instead of fubing or other kinds of militia. The shi institutions were existing almost every aspect of governmental affairs, and the political power was mainly centralized in the Zhongshu-menxia (中書門下) operating by the prime ministers. Although the strength of the Tang Empire was substantially improved, Emperor Xuanzong was so confident of his military ability and skill in controlling subordinates that he gradually ignored to check and balance the power of his jiedushis, who owned a lot of power in both military and political aspects in their commanding regions, and frequently appointed one general to be two or even more jiedushis at the same time. At last one of this kind of jiedushi An Lushan (安祿山) launched a massive rebellion, crashing Emperor Xuanzong’s excessive confidence and tearing the cracks of the empire even more enormous.