中共與北朝鮮在戰後相互幫助，醞釀中的亞洲共產黨情報局構成了他們之間同盟的基礎。在史達林的支持下，金日成搶先發動了戰爭，而毛澤東決定推遲《中朝同盟條約》的簽訂。為了儘快結束朝鮮戰爭，毛澤東急於派兵入朝作戰，金日成反覆多變，在莫斯科的沉默下拒絕中國出兵援助，毛澤東在極其困難的條件下決心孤軍對美作戰。戰爭期間，莫斯科在主要戰略問題上都支持中國的主張，金日成感到屈辱和壓抑。朝鮮戰爭結束後，金日成開始傾向於朝鮮的獨立發展，並首先肅清黨內的異己力量。中共與金日成在對朝鮮勞動黨內延安派的處理問題上發生衝突，中朝同盟陷入危機。蘇共二十大以後中蘇之間開始出現分歧，毛澤東需要朝鮮的支持，從而對金日成採取了容忍的態度，甚至主動提出從朝鮮撤軍，中朝關係得以改善，並於1961 年簽訂了雙邊條約。中朝同盟並不是他們自己宣傳的「唇齒相依」的關係，而是內部充滿矛盾的極不穩定的「政治聯姻」。

Mutual aid between the Chinese Communist Party (CCP) and North Korea in the wake of World War II, especially the proposed Asian Communist Intelligence Bureau, formed the foundation of the Sino-Korean alliance. With Joseph Stalin’s support, Kim Il-sung launched war against South Korea in 1950. In response, Mao Zedong decided to postpone the signing of the Sino-Korean alliance treaty. In order to end the war as soon as possible, Mao was anxious to dispatch Chinese troops to Korea. Kim was ambivalent and even rejected Mao’s initial offer with the acquiescence of Moscow. Mao, however, was determined to fight the Americans regardless of whether the Soviets agreed. After China entered the war, Stalin sided with Mao on all major strategic issues, which made Kim feel slighted and alienated. After the end of the war, Kim went to considerable lengths to stress North Korea’s independence and began to purge his opponents within the Korean Workers’ Party. The CCP strongly disagreed with Kim’s handling of the Yan-an faction, and this threatened to destroy their alliance. Mao, however, needed North Korea due to the increasing Sino-Soviet divergence following the Twentieth Congress of the Soviet Communist Party. He thus took a conciliatory stance toward Kim and even initiated the proposal to withdraw the Chinese troops from North Korea. Sino-North Korean relations thus improved, and the two parties signed a bilateral treaty in 1961. This article concludes that the Sino-North Korean relationship was far from the alliance of “teeth and lips” portrayed in the propaganda of the day, but an unstable, conflict-ridden political marriage of convenience.