Brandt, like many young radicals, was critical of the leadership of people like Rudolf Breitscheild. In 1931 he helped form Socialist Workers Party (SAP), a Marxist left-wing organization. By October 1931 SAP claimed to have over 50,000 members.
In February 1937, Brandt travelled to Spain to cover the Spanish Civil War. He based himself in Barcelona where he developed close links with the Worker's Party (POUM). While covering the war he developed a life long suspicion of communism. He later recalled how the "POUM were persecuted, dragged before the courts, or even murdered by the Communists."
On his return to Norway he wrote about the dangers for socialists working with Joseph Stalin and the Soviet Union. After the signing of the Nazi-Soviet Pact he wrote: " It is hardly a novel situation to find the leaders of the Soviet Union in a state of outright war against the socialist movement. It has happened before. But today the whole movement is obliged to stand up and fight, and draw a clear dividing line between itself and the Soviet Union. It is not the socialist movement but the Soviet Union which has changed. It is not the socialist movement but the Soviet Union which has entered a pact of friendship with Nazism.
A socialist, Brandt became chairman of the Sozialdemokratische Partei Deutschlands (SPD) in 1964. Two years later he joined the coalition government led by Kurt Kiesinger. Brandt, as Foreign Minister, developed the policy of Ostpolitik (reconciliation between eastern and western Europe).
Brandt was a strong supporter of Britain joining the European Economic Community. In December 1967 he argued "Our own interest, which it is up to us to represent, and our understanding of the state of European interests, obliges us to speak a clear language and urge our French neighbours not to make things too difficult for themselves and others."
In 1969 Brandt became Chancellor of Federal Republic of Germany (West Germany). He continued with his policy of Ostpolitik and in 1970 negotiated an agreement with the Soviet Union accepting the frontiers of Berlin. Later that year he signed a non-aggression pact with Poland.
The Basic Treaty was signed in 1972. In this treaty the Federal Republic of Germany and German Democratic Republic committed themselves to developing normal relations on the "basis of equality, guaranteeing their mutual territorial integrity as well as the border between them, and recognizing each other's independence and sovereignty".
Brandt was forced to resign as Chancellor in April 1974 after it was discovered that his close political aide, Gunther Guillaume, was an East German spy.
Brandt continued to be active in politics and between 1977 and 1983 was chairman of the Brandt Commission on economic development. Its report, North-South: A Programme for Survival, argued that the rich north should help countries in the poor southern hemisphere.
Willy Brandt died in 1992.