長江上游地區戰爭頻繁、內政失序，四川省幾乎到處充斥著毫無紀律的軍隊與流竄危害的土匪；可是無論是北京的中央政府，抑或四川的地方軍事與民政當局，既無心也無力保護外商利益。值此危急時刻，美國海軍只能挺身而出，肩負起確保航行安全、維護美國利益與尊嚴的重責大任。然而，當美國海軍執行護航任務時，往往卻又陷入該盡力克制、避免干涉中國內政，或是該斷然採取武力反擊行動之間的兩難處境。此乃肇因於美國在中國的外交政策，一方面帶有理想性，試圖尊重中國的主權獨立與完整，不希望以帝國主義方式在中國獲得權力或財富，也極力避免違反中立原則，過份涉入中國內政事務；另一方面，則如同英、法、日等其他國家一樣，從國際現實角度著眼，難免帶著擴張勢力版圖、維護商業利益的色彩成分，也較易陷入以保衛國家尊嚴之名的武力干涉。美國海軍在長江上游護航問題爭議上的作為與處置之道，即清楚反映其在理想與現實之間徘徊搖擺的雙重特性。 In the 1920s civil wars and disorder on the upper Yangtze made Szechuan a province where unruly soldiers and wayward bandits dominated. Neither the central government in Peking nor local authorities in Szechuan intended to or was able to protect foreign interests. Thus the U.S. Navy had no choice but to assume responsibility for maintaining shipping security to shield American interests and prestige. However, the U.S. Navy faced the dilemma of not being able to interfere in Chinese internal affairs or resorting to use of force when carrying out its patrolling and convoy missions. This paper finds that U.S. foreign policy towards China possessed contradictory characteristics: on one hand, U.S. policy was idealistic as it focused on respecting the independence and integrity of Chinese sovereignty; while on the other hand, realism came to the fore as the U.S. sought to expand and defend American business interests. The U.S. Navy’s responses and operations on the upper Yangtze is an obvious exhibition of this kind of wavering between idealism and realism.