發生於元豐五年(1082)的永樂城戰役，在後代的紀錄中被普遍視為一場影響深遠的慘敗，由於宋軍遭受重大的傷亡，導致神宗放棄對西夏用兵的政策，並因此鬱鬱而終。不過，在傳世的北宋文獻中，對於此一戰役的描述存有很大的差異。本文從探討此役發生的背景和過程入手，透過考證傳統說法的真質性，指出元祐時代主政官員的說法，深刻影響了後世對永樂之役的印象。這些反對神宗拓邊政策的官員，刻意誇大了此役所造成的人員損失及後績影響，其目的不僅在於打擊主戰的官員，更是要強調神宗因永樂之敗放棄對西夏用兵的政策，以合理化他們與西夏和談的主張。也就是說，政治立場是形塑此一戰役紀錄的重要因素。事實上，由於反戰論的盛行，北宋時代的戰爭紀事往往存在強調己方損失，忽略軍事成果的特殊現象，永樂城之役的相關紀事即為其中一例。

Traditionally, Chinese historians consider the Yongle 永樂 campaign of 1082 to have been a heavy defeat for the Song armies with far-reaching consequences. After suffering a huge number of losses, the Emperor Shenzong 神宗 decided to abandon the offensive in Xixia 西夏, resulting in the grief-stricken emperor's subsequent illness and death. However, examining surviving descriptions of the Yongle campaign in records kept by Song officials reveals considerable differences. This article begins by exploring the background and course of the campaign, verifies the authenticity of traditional accounts, and argues that the writings of certain senior government officials have deeply influenced later generations' impressions of this campaign. These officials, opposed to Shenzong's border expansion policy, intentionally exaggerated the Song armies' losses in the Yongle campaign and their after-affects. This was not merely intended to oppose those officials advocating war, but more importantly to emphasize the fact that it was due to this defeat that Shenzong abandoned his policy of offensives against the Tangut, thus giving currency to the policy of a return to peace talks. More succinctly, political bias influenced how the Yongle campaign was recorded. Due to the popularity of anti-bellicose opinion, Song army losses tend to be emphasized and military gains downplayed in the war chronicles of the Northern Song, an example of which is the record of the Yongle campaign.