Construction began on the initiative of President Josip Broz Tito, who called the project the "Road of brotherhood and unity" after the motto of the League of Communists of Yugoslavia. The first section between Zagreb and Belgrade was built with the effort of the Yugoslav People's Army and volunteer Youth Work Actions and was opened in 1950. The section between Ljubljana and Zagreb was built by 54,000 volunteers in less than eight months in 1958. The southern section from Belgrade was not completed until the mid-1960s. Its importance caused it to be colloquially named autoput or autocesta. This use has since largely faded out, after the successor states built further motorways. In the 1960s and 1970s the autoput became a much frequented holiday route for Turkish immigrants in West Germany and Austria visiting their original homeland during the summer vacation time, and for tourists to southeastern Europe. Entering communist but non-aligned Yugoslavia was far easier, for people from NATO countries such as West Germany and Turkey, than entering any of the Warsaw Pact communist countries of the Balkan region that might have provided alternative routes. Originally an ordinary road, the carriageway used to be congested with cars and trucks, especially in summertime, when overtired long-distance drivers caused numerous accidents. Wrecked cars usually remained in place for long periods of time, providing a grim reminder of the dangers of the highway. The situation slightly improved after some parts were brought up to modern motorway standards on the following sections built between 1977 and 1991:
In 1991, several sections were affected by the Yugoslav wars, bringing severe damage, and causing the traffic to be almost completely discontinued in places.
European route E70: Ljubljana–Zagreb–Sisak–Slavonski Brod–Belgrade
European route E75: Belgrade–Niš–Skopje-Veles–Thessaloniki
Legacy
Since 1994 the route is also part of the Pan-European corridor X that extends from Salzburg to Thessaloniki. The road has been continuously upgraded. As of 2019, it is a modern motorway in its entire length through:
The most difficult section to engineer and build was the Grdelica Gorge section which was completed in May 2019. The classification as the M-1 Highway continued in Serbia up to 2013, when the road was reorganized as the A1 and A3.