19 August 1968
Nigeria's Federal Troops launched a major offensive against multiple targets in Biafra on the 19th of August 1968. Despite claims that scores of people were killed, the leader of the Nigerian military government, General Yakubu Gowon said that his troops were 'behaving correctly'. Biafra had declared itself independent from Nigeria on 30 May 1967 which sparked tensions. The root of the conflict was economic, ethnic, cultural and religious tensions among the various peoples of the country. Like many other African countries, Nigeria was an artificial construct initiated by the British who ignored religious, linguistic, and ethnic differences in the region. The country was eight years into its independence which it gained from Britain in 1960. At the time of the civil war the official population of Nigeria was 60 million consisting of nearly 300 different ethnic and cultural groups.
References

Tebyan.net,  2010. ‘Nigerian Civil War Begins’ [online] Available at www.tebyan.net [Accessed: 18 July 2011]|

Boddy-Evans, A., 2011. ‘This Day in African History 19 August’ from African History [online] Available at www.africanhistory.about.com [Accessed 18 July 2011]