歷來討論魏、蜀、吳三國關係的論著多著眼於蜀、吳聯合抗魏。本文嘗試以吳國為本位，分析孫吳政權 (西元200-280年) 如何在當時的「國際」環境下，透過推行「彈性外交」以求取生存空間。所謂「彈性外交」是指孫吳並不囿於固定路線，伺機而動的一種外交策略。孫吳得以施行「彈性外交」的原因可以從兩方面分析。一、「國際秩序」的結構性因素：即1.魏國一時不能滅吳，對吳國的反覆無可如何；2.蜀漢既無力滅魏，又需要吳國作為盟友，只好作出容讓；3.吳國缺乏進行統一的正統論基礎，弊處在於與魏、蜀相比時不能提出鮮明的正統理論，需要依違其間，好處卻在於吳國因而缺少了正統論的包袱，可以隨利益而改變立場。二、國內政治因素，即1.吳國長期受山越困擾，需要安定內部；2.吳國發展出「保江東、觀成敗」的立國觀念，在保守江東的基礎上，為生存、發展可因應時勢而改變外交立場。

This paper argues that the kingdom of Wu (200-280) adopted a unique diplomatic strategy, which the author refers to as “elastic diplomacy,” to survive. This strategy stresses having the flexibility to respond to changing circumstances and exploit available opportunities. In practice, the Wu would act as a client state of the Wei dynasty (220-265) or an ally of the Shu Han state (221-264), depending on its own interests. This paper traces the implementation of this strategy and concludes that its efficacy was influenced by several external and domestic political factors. The Wei and the Shu were long-time rivals that competed for the cooperation of the Wu and the right to lay claim to being the legitimate successor to the Han dynasty. The Wu, on the other hand, devoted all of its resources to suppressing the mountainous Yue people and were continually affected by the policy of flexibility formulated by Sun Ce (孫策 184-200), the founder of the regime.