Paasikivi joined the conservative Old Finnish Party, later renamed the National Coalition Party, and was elected to parliament in 1907. He served briefly as prime minister of the newly independent Finland in 1918, at which point he supported a monarchy and left government service.
As World War II loomed, Paasikivi returned to government work, serving as ambassador to Sweden during 1936–1940 and then ambassador to the Soviet Union during 1940–1941. He adopted a more compliant attitude toward the Soviets than his government in general demonstrated. After the end of the Continuation War (1941–1944) with the Soviet Union, Paasikivi was one of the few Finnish politicians who continued to enjoy his country's confidence. He was appointed prime minister in November 1944, serving under President Carl Mannerheim, and in March 1946 was elected president of Finland upon Mannerheim's resignation. Paasikiivi was elected to office in his own right in February 1950. In the February 1956 election, in spite of his advanced age, he reluctantly offered himself as a candidate in the second ballot and was ultimately elected because of a split vote among competing parties.
As president, Paasikivi stood generally aloof from party politics and became a true champion of his country. Guided by what he viewed as "small state realism," he deserves credit for protecting Finnish democracy during the Cold War in spite of its recognized geopolitical position in the Soviet sphere of influence. He was successful in maintaining Finnish independence by means of an accommodating policy toward the Soviet Union, insisting that Finland was a "capitalist friend."
In his capacity as the leading Finnish politician in the immediate post–World War II years, Paasikivi developed the so-called Paasikivi Line, aimed at inspiring trust in Moscow on the assumption that Soviet interest in Finland was of a strategic nature and not ideologically driven. Thanks to his pragmatic realism and tactical skills, he carefully balanced the need to be obliging in questions of vital concern to the Soviet Union while remaining uncompromising on Finnish essentials, most importantly its autonomy and democracy. Paasikivi died in Helsinki on 14 December 1956, only months after his reelection.
Rintala, Marvin. Four Finns: Political Profiles. Berkeley: University of California Press, 1969.; Tuominen, Uuno. J. K. Paasikivi: A Pictorial Biography. Helsinki: Otava, 1970.