In the late 1980s, Slovenia embarked on a process of democratic reform, which went unparalleled in the other five Yugoslav republics. The Slovenian communist leadership, under Milan Kučan, was allowing an ever greater degree of freedom of the press. The magazine Mladina was taking advantage of this and became extremely popular in Slovenia, deliberately testing the borders of press freedom with news and satire breaking old taboos. In 1987 it started more and more frequently attacking the Yugoslav People's Army (YPA) and its leadership, for instance labeling the defense minister, Branko Mamula, a "merchant of death" for selling arms to famine-stricken Ethiopia. Many of the articles were written by the young defense expert Janez Janša, who soon became a particular irritant for the YPA leadership. As far as the YPA were concerned, Mladina were attacking the army, the main protector of Yugoslav unity, and hence attacking Yugoslavia itself. When they realized that the Slovene government were not going to crack down on Mladina, they decided to do so themselves.
In 1988, Mladina got its hands on notes from a secret meeting of the central committee of the League of Communists of Yugoslavia, detailing plans for arrest of journalists and dissidents in Slovenia. Their possession of these documents gave the YPA the pretext it needed. Shortly after, on 31 May, Janša, another Mladina-journalist David Tasić and a Slovene sergeant in the YPA Ivan Borštner were arrested. Later the editor of Mladina Franci Zavrl was also arrested. They were charged with betraying military secrets, a charge that would have to be tried in a military court. Thus the government of Slovenia had no involvement in the proceedings.
The trial was held in camera, and the nature of the documents the accused were supposed to have revealed was never officially made public, giving rise to a plethora of rumors, and to the widespread assumption that the whole trial was a frame-up to get even with Janša and Mladina. In addition, the Army made the decision to hold the trial in the Serbo-Croatian language rather than Slovenian, in spite of provisions in the Slovene republican constitution that all official business in Slovenia should be conducted in the Slovene language. This further outraged Slovenian public opinion, to which the use of the Slovenian language was of great symbolic significance. The four accused were sentenced to between six months and four years imprisonment, and handed back to the Slovene authorities, which carried out the sentences in the mildest way possible. Zavrl later related how "I spent my days editing the magazine in my office and my nights in prison. On one occasion, when I was late getting back, I had to break into the prison over the wire!"