An express train carrying foreign workers from Yugoslavia to West Germany derailed in Zagreb, killing 153 people.

Gastarbeiter are foreign or migrant workers, particularly those who had moved to West Germany between 1955 and 1973, seeking work as part of a formal guest worker program. As a result, guestworkers are generally considered temporary migrants because their residency in the country of immigration is not yet determined to be permanent. Other countries had similar programs: in the Netherlands and Belgium it was called the gastarbeider program; in Sweden, Denmark and Norway it was called arbetskraftsinvandring (workforce-immigration); and in East Germany such workers were called Vertragsarbeiter. The term that was used during the Nazi era was Fremdarbeiter. However, the latter term had negative connotations, and was no longer used after World War II.

Yugoslavia was a country in Central Europe and the Balkans that existed from 1918 to 1992. It came into existence following World War I, under the name of the Kingdom of Serbs, Croats and Slovenes from the merger of the Kingdom of Serbia with the provisional State of Slovenes, Croats and Serbs, and constituted the first union of South Slavic peoples as a sovereign state, following centuries of foreign rule over the region under the Ottoman Empire and the Habsburg monarchy.

West Germany was the common English name for the Federal Republic of Germany (FRG) from its formation on 23 May 1949 until its reunification with East Germany on 3 October 1990. It is sometimes known as the Bonn Republic after its capital city of Bonn, or as the Second German Republic. During the Cold War, the western portion of Germany and the associated territory of West Berlin were parts of the Western Bloc. West Germany was formed as a political entity during the Allied occupation of Germany after World War II, established from 12 states formed in the three Allied zones of occupation held by the United States, the United Kingdom, and France.