members as of end-1970. DİSK leaders were again arrested after the military intervention on 12 March 1971, and the work of the confederation slowed down markedly during this period. Yet, further trade unions joined DİSK, raising the total membership of the confederation to 270,000 as of 1973. The period after the fifth congress (21–24 May 1975) witnessed a boost in the popularity of DİSK, which now counted 25 members. The most important growth occurred with the affiliation of the former Türk-İş member Genel-İş under the leadership of Abdullah Baştürk. By this time the membership of DİSK was close to 600,000. In 1977 participation to the First of May demonstration organized by DİSK was even larger than the previous year, but the peaceful demonstration ended in a blood bath when unknown persons opened fire to the crowd toward the end of the rally and 35 people were killed. On the 6th congress of the confederation that was held on 22–26 December 1977 Abdullah Baştürk was elected as the head of DİSK. Fehmi Işıklar became the secretary general. In 1978 DİSK organized a First of May rally again in Taksim Square and there was a large participation in spite of the bloody events of the previous year. By 1979 martial law had expanded to cover also Istanbul, and the First of May celebrations were held in Izmir, while in 1980 the celebrations were totally banned. On 22 July 1980 the founder of DİSK and chairman of Türkiye Maden-İş, Kemal Türkler was killed in front of his house in Merter, Istanbul. The public prosecutor in Bakırköy indicted the alleged right-wing militants Ünal Osmanağaoğlu, Aydın Eryılmaz, Abdülsamet Karakuş and İsmet Koçak for being involved in the murder. Bakırköy Heavy Penal Court 2 twice decided on acquittal of Osmanağaoğlu. Each time the Court of Cassation quashed the verdict. On 1 December 2010 Bakırköy Heavy Penal Court 2 ruled that the case had to be dropped because of lapse of time. Before the 1980 coup, four main trade union federations with differing political orientations dominated the labor scene. The main union organization, the Confederation of Turkish Trade Unions (Türkiye İşçi Sendikaları Konfederasyonu—Türk-İş) was politically moderate, adhering to legal limits on its activities. The other major union group, the Confederation of Progressive Trade Unions of Turkey (Türkiye Devrimci İşçi Sendikaları Konfederasyonu—DİSK), originated from a faction of Türk-İş in 1967. DİSK was much smaller than Türk-İş but more