威廉•C•布利特对苏联的认识在1918年到1946年间经历了巨大的转变。早在1918年，布利特就曾建议美国承认列宁领导的苏维埃政权。在凡尔赛和会召开期间，布利特还曾秘密赴俄，与苏维埃政府进行和平谈判。这一时期的布利特认为，俄国的十月革命旨在使俄国人民摆脱压迫和专制、获得自由和民主，他甚至将十月革命看作与法美资产阶级革命类似的事件，将革命后建立的苏维埃政权看作是美国民主实验的继续。基于这一认识，在此后的十数年间，布利特一直倡导建立美苏间友好关系、将苏联纳入美国领导的自由世界。然而，两年半的驻苏大使任期却逐步改变了布利特对苏联的认识。在苏联度过的头一年让布利特初尝建立美苏间友好关系这一使命的艰辛与不易。在布利特看来，苏联的秘密警察会不分昼夜地对美国大使和使馆进行监控；苏联政府亦是不顾口头承诺，一再失信：美国大使的飞机出行受限，大使馆人员需要靠走私取得卢布，美国未能在事先敲定的地方修建新大使馆。美苏债务谈判的失败更是令布利特大失所望。这时，威廉•C•布利特开始意识到他在1919年看到的只是大革命产生的幻象，苏联并没有沿着美国式的民主和自由向前发展。此时的他认为，苏联是一个专制独裁的政权；苏联治下的人民毫无自由可言，终日生活在恐惧中，而未来的苏联也不会发生积极的改变。虽然这位美国大使的苏联观念发生了上述变化，但他对建立美苏友好关系并没有完全丧失信心。1935年的莫斯科生活却令布利特彻底放弃了与苏联建立友好关系的努力。这年7月，共产国际在莫斯科召开会议。布利特将这次会议的召开解读为苏联再次背弃对美国的承诺，继续利用美国共产党和工人运动干涉美国内政，意图推翻美国政府。之后，苏联领导人又明确告知美国大使他们对于和美国建立真正友好的关系并不感兴趣。从此以后，布利特变成了彻底的反苏反共主义者。他认为，苏联从未放弃在世界范围内推行共产主义革命的目标；和纳粹德国一样，苏联是资本主义自由世界和世界和平的主要威胁；自由民主国家应该在美国的领导下，共同抵制苏联的共产主义侵略。导致威廉•C•布利特的苏联认识发生转变的原因既包括他个人的因素，也与这一时期美苏关系发展的大趋势密切相关。布利特的性格过于感性，缺乏耐心，好走极端，容易产生失望情绪。不仅如此，布利特没有接受过外交专业人员的职业训练，任职前对苏联缺乏了解，就任后在分析问题时主观性过强，不够理性。与此同时，由于意识形态存在差异，美苏两国严重缺乏互信。在此基础上制定的外交政策导致这一时期的美苏关系趋于冷淡。虽然他的苏联认识发生了重大转变，但是威廉•C•布利特追求的终极目标却从未改变。布利特始终坚信应该建立一个以美国为领袖的自由世界，只有这样才能确保世界的永久和平。

From 1918 to 1946，William C. Bullitt’s Soviet perception underwent great changes. As early as 1918, Bullitt recommended that American government should recognize Soviet Russia led by Lenin. During the peace conference at Versailles, Bullitt had been secretly sent to Russia. He held peace negotiation with the Soviet government, and bought back a draft peace plan. During this period, Bullitt believed that the October revolution and the Soviet regime in Russia aimed at overthrowing tyranny and gaining freedom and democracy for the Russian people. He even regarded the October Revolution as something similar to the French Revolution and American independence war, and saw Soviet Russia as a sort of continuation of American democratic experiment. With this understanding, Bullitt had advocated that the U.S should build friendly relationship with the Soviet Union, and make this regime fit into the liberal world led by America. However，his two and half year in Moscow changed his view of the Soviet Union gradually. The first year made him realize that it was really hard to complete his mission of building friendly Soviet-American relations. From Bullitt’s point of view, the Soviet secret police would keep watch on him and the American embassy day and night and the Soviet government would never take their oral promise seriously. His staff of the embassy got the rubbles by patronizing the Black Bourse. Besides, Bullitt failed to get the property Stalin had offered to him to construct a new American embassy. What’s more, to his great disappointment, the Soviet-American debt negotiation came to nothing. At this time, Bullitt learned that what he had seen in 1919 was mere the fantasy produced by the great October Revolution and the Soviet Union did not follow the way of democracy and freedom on the American Model. He regarded the Soviet Union as a regime of tyranny and autocracy. To him, Soviet citizens lived in a state of terror without any personal freedom, and no positive changes would occur to future Soviet Russia. Although his concept on the Soviet Union changed, he still had confidence in building friendly Soviet-American relations.Nevertheless, Bullitt gave up his effort of forming amicable relations with the Soviet Union in 1935. The Seventh Communist International met in July, 1935. Bullitt saw this convention as the newest Soviet breach of faith and the interference in American internal affairs. He believed that this meeting aimed at overthrowing American Government by urging American Communists to continue agitation for class warfare. Later Bullitt was told that the Soviet Union did not have any interest in friendly Soviet-American relations. From then on, Bullitt became a pursuit of anti-Soviet and anti-communist. He believed that the Soviet Union never gave up its goal of world revolution and it was the major threat to the liberal world and the world peace just like Nazi Germany. He called on all the liberal democracies under the leadership of America to resist Soviet communism aggression jointly. Many factors led to William C. Bullitt’s perception transformation of the Soviet Union, including both his personal character and experience and the tendency of the Soviet-American relations in this period. Bullitt was too emotional and impatient, which made him particularly susceptible to disappointment. Moreover, He did not receive much professional training of being a diplomat. Before he accepted the appointment, Bullitt did not know much about Russia, and after became the first American ambassador to the Soviet Union, he could not comprehend these issues in a reasonable way. Meanwhile, the ideological differences resulted in a serious lack of mutual trust between the US and the Soviet Union. The diplomatic policy made on this basis led to the frosty Soviet-American relations. Although his Soviet understanding converted, William C. Bullitt always believed that a liberal world led by the United States should be set up, and this was the only way to ensure the world peace.