 The Apprentice Boys ' parade is an annual celebration by unionists of the relief of the Siege of Derry in 1689 , which began when thirteen young apprentice boys shut the city 's gates against the army of King James . At that time the parade was held on 12 August each year . Participants from across Northern Ireland and Britain marched along the city walls above the <unk> , and were often openly hostile to the residents . On 30 July 1969 the Derry Citizens Defence Association ( <unk> ) was formed to try to preserve peace during the period of the parade , and to defend the <unk> and <unk> in the event of an attack . The chairman was Seán Keenan , an Irish Republican Army ( IRA ) veteran ; the vice @-@ chairman was Paddy Doherty , a popular local man sometimes known as " Paddy <unk> " and the secretary was Johnnie White , another leading republican and leader of the James Connolly Republican Club . Street committees were formed under the overall command of the <unk> and barricades were built on the night of 11 August . The parade took place as planned on 12 August . As it passed through Waterloo Place , on the edge of the <unk> , hostilities began between supporters and opponents of the parade . Fighting between the two groups continued for two hours , then the police joined in . They charged up William Street against the <unk> , followed by the ' <unk> ' . They were met with a hail of stones and petrol bombs . The ensuing battle became known as the Battle of the <unk> . Late in the evening , having been driven back repeatedly , the police fired canisters of CS gas into the crowd . Youths on the roof of a high @-@ rise block of flats on Rossville Street threw petrol bombs down on the police . <unk> @-@ talkies were used to maintain contact between different areas of fighting and <unk> headquarters in Paddy Doherty 's house in Westland Street , and first aid stations were operating , staffed by doctors , nurses and volunteers . Women and girls made milk @-@ bottle crates of petrol bombs for supply to the youths in the front line and " Radio Free Derry " broadcast to the fighters and their families . On the third day of fighting , 14 August , the Northern Ireland Government mobilised the Ulster Special Constabulary ( B @-@ Specials ) , a force greatly feared by nationalists in Derry and elsewhere . Before they engaged , however , British troops were deployed at the scene , carrying automatic rifles and sub @-@ machine guns . The RUC and B @-@ Specials withdrew , and the troops took up positions outside the barricaded area . 
