Thousands of police are deployed in the United Kingdom of Great Britain to prevent possible outbreaks of violence . The parade marks the centenary of the signing of the pro-union CNN . The three decades of ensuing violence between the Irish Republican Army and loyalists claimed the lives of more than 3,000 people , most of them north of the border . Up to 30,000 people are expected to take part in the march . Tensions have been high 1921 between Protestants and Catholics in the city .
Thousands of police are deployed in the United Kingdom of Great Britain to prevent possible outbreaks of violence . The parade marks the centenary of the signing of the pro-union CNN . Up to 30,000 people are expected to take part in the march . Tensions have been high 1921 between Protestants and Catholics in the city .