羅馬帝國的衰落
朝政
  羅馬帝國不斷收到來自北歐的襲擊,而羅馬最終於476年陷落。西羅馬帝國的最後一個羅馬皇帝羅慕路斯·奧古斯都嚮日耳曼首領奧多亞塞投降。英國歷史學家愛德華·吉本在《羅馬帝國衰亡史》(1776)中認為羅馬人墮落了,喪失了公民的美德。吉本說相信死後可享永生的基督教使人懶惰與冷漠,至今仍然如此。格倫·布沃肖剋評論說:“從18世紀以後,我們對羅馬衰亡耿耿於懷:它被看作是所有已知的衰落的原型,而且因此成為我們擔憂自身的象徵。”它仍然是最大的歷史謎團之一,傳統上擁有龐大的研究學者隊伍。
  
  另外一些值得註意的時期如378年的阿德裏安堡戰役,395狄奧多西一世(羅馬帝國最後一次政治統一)逝世,406年日耳曼人在羅馬軍團撤回意大利阻擋亞拉裏剋一世時跨過萊茵河,408年斯提利科去世,以及隨後的西羅馬軍團瓦解,565年最後一位嘗試收復西羅馬的查士丁尼一世去世,以及632年伊斯蘭教入侵。很多學者堅持認為比起“衰亡”來這些變化更適合被描述成一次復雜的轉變。隨着時間流逝關於羅馬帝國為何衰亡或者是否真的衰亡了提出了很多理論。


  The Roman Empire had been repeatedly attacked by invading armies from Northern Europe and in 476, Rome finally fell. Romulus Augustus, the last Emperor of the Western Roman Empire surrendered to the Germanic King Odoacer. British historian Edward Gibbon argued in The Decline and Fall of the Roman Empire (1776) that the Romans had become decadent, they had lost civic virtue. Gibbon said that the adoption of Christianity, meant belief in a better life after death, and therefore made people lazy and indifferent to the present. "From the eighteenth century onward", Glen W. Bowersock has remarked, "we have been obsessed with the fall: it has been valued as an archetype for every perceived decline, and, hence, as a symbol for our own fears." It remains one of the greatest historical questions, and has a tradition rich in scholarly interest.
  
  Some other notable dates are the Battle of Adrianople in 378, the death of Theodosius I in 395 (the last time the Roman Empire was politically unified), the crossing of the Rhine in 406 by Germanic tribes after the withdrawal of the legions in order to defend Italy against Alaric I, the death of Stilicho in 408, followed by the disintegration of the western legions, the death of Justinian I, the last Roman Emperor who tried to reconquer the west, in 565, and the coming of Islam after 632. Many scholars maintain that rather than a "fall", the changes can more accurately be described as a complex transformation. Over time many theories have been proposed on why the Empire fell, or whether indeed it fell at all.