( CNN ) -- Thousands of people are expected to march in Northern Ireland on Sunday to commemorate the 1972 Bloody Sunday massacre of local people by British troops . Organizers expect it to be the last march of its kind , since the British government finally admitted last year that its troops , not the demonstrators , were to blame . `` The great lie has been laid bare . The truth has been brought home at last , '' the republican political party Sinn Fein said in a statement Sunday . Sinn Fein seeks for Northern Ireland to become part of the Republic of Ireland , rather than the United Kingdom . In June , the British government released a damning report that reversed decades of official explanations for the 1972 killings . The paratroopers who killed 14 people had no reason to believe they were under threat from the victims , gave no warnings before firing and lied to the far-reaching official inquiry into the seminal event , the inquiry concluded . Its report was a comprehensive rejection of the British government 's official account of the killings , which had stood for 38 years . `` Some members of our armed forces acted wrongly ... and for that , on behalf of the government -- indeed , on behalf of our country -- I am deeply sorry , '' British Prime Minister David Cameron said after the release of the long-awaited report . Bloody Sunday took place in the single bloodiest year of a conflict that claimed about 3,000 lives over a three-decade period known locally as The Troubles . The killings strengthened the Provisional Irish Republican Army , increased Irish Catholic hostility towards the British army and `` exacerbated the violent conflict of the years that followed , '' its report found . Sinn Fein is closely associated with the PIRA , which laid down its arms as part of a 1998 peace agreement . British troops fired more than 100 rounds on Bloody Sunday , in violation of orders issued to every soldier serving in Northern Ireland at the time , the report found . There was some provocation by the IRA in Londonderry that day , but nothing that justified the shootings of civilians , the report found . Only one victim was associated with the IRA , and he was probably not posing a threat when he was fatally shot , the report found . Bloody Sunday has been considered by many as one of the greatest injustices of Northern Ireland 's troubled history . Even the name of the city where it happened is disputed , with pro-Irish nationalists calling it Derry and pro-British unionists calling it Londonderry . Addressing the question of how high responsibility for the massacre should go , the report overwhelmingly placed it with the soldiers who were on the ground , along with their commander , Lt. Col. Derek Wilford , who decided to launch the incursion . The report said there is no evidence that either the British or Northern Irish governments `` intended , planned , or foresaw '' the events of that day , or that either government tolerated or encouraged the use of `` unjustified '' lethal force . CNN 's Richard Allen Greene , Phil Black and Melissa Gray contributed to this report .
Sunday marks the 39th anniversary of the massacre in Northern Ireland . A report last year found British troops were to blame for the killing of 14 people . That reversed decades of official explanations . Sinn Fein : `` The truth has been brought home at last ''