Key dates of the Troubles: 50 years on from British soldiers arriving in North
Since soldiers first appeared on Northern Ireland's streets on August 14 1969, the Army witnessed and was involved in some of the darkest hours of the Troubles.
A total of 722 soldiers died during Operation Banner, which ran from 1969 to 2007.
The Army was also accused of murdering civilians during those decades of bloodshed.
To some, troops were peacekeepers who helped in the battle to maintain law and order as the region teetered on the brink of civil war; to others they were an occupying force who used violence indiscriminately against nationalists and republicans, with rogue members even working in cahoots with loyalist paramilitaries.
Ahead of the 50th anniversary of the start of Operation Banner, these are some of the key dates in those years of conflict:
In August, troops were brought in after police were faced with inter-community rioting in Londonderry and west Belfast. The loyalist marching season sparked violence in Derry in July but the worst rioting occurred in August following the annual Apprentice Boys march in the city.
After three days of confrontation, known as the Battle of the Bogside, the UK government agreed that British troops could be deployed. A broad swathe of Catholic opinion, including the church and the old Nationalist party accepted the presence of the Army. They saw it as necessary for restoration of law and order and defence of Catholic areas in Derry.
The first serious clashes involved troops in riots in Ballymurphy, west Belfast. General Officer Commanding Sir Ian Freeland warned soldiers would shoot to kill at anyone holding petrol bombs or guns. In July, a military curfew on the Falls Road sparked a gun battle with the Official IRA which marked an end to the Army's "honeymoon" period. Army actions caused six deaths.
In February, the IRA shot and killed the first soldier and Major James Chichester Clark resigned as Northern Ireland prime minister after Edward Heath refused his request for more troops. A total of 44 soldiers and five locally-recruited Ulster Defence Regiment members died. The Army killed 45.
Ten civilians were killed in three days of shooting in the Ballymurphy area of west Belfast as paratroopers moved in to republican strongholds after the introduction of the controversial state policy of internment without trial.
In January, paratroopers shot 13 demonstrators dead during a march for civil rights in Londonderry. The event became known as Bloody Sunday, galvanised IRA recruitment, and was condemned around the world. The Irish government lodged protests and rioters burned the British Embassy in Dublin.
The Official IRA revenge bombing of the Aldershot headquarters of the Parachute Regiment, which carried out the Derry shootings, killed several civilians.
In July, following the Bloody Friday slaughter in Belfast city centre from more than 20 IRA bombs, the Army moved into Derry's Bogside no-go area and more IRA bombings followed. Operation Motorman, an Army strategy to end republican no-go areas, was launched and there were 21,000 troops in the province.
In May, troops were called upon to distribute petrol after the hard-line Ulster Workers' Council, an organisation heavily influenced by paramilitaries, called a stoppage of loyalists working at power stations in protest at powersharing with nationalists. The Stormont coalition collapsed and ministers were accused of not using the Army soon enough by those opposed to the direct action.
The government announced the deployment of extra troops after 10 Protestant workers were killed by the IRA at Kingsmill, Co Armagh. In May, a private at Fort George, Co Londonderry, shot and killed a 20-year-old Catholic while he was sitting on a bus.
In August, an IRA landmine and shooting ambush at Narrow Water, Warrenpoint, Co Down, killed 18 soldiers. An 800lb bomb detonated in a trailer at the side of the road near Carlingford Lough, the boundary with the Republic.
IRA men watching from the southern shoreline opened fire, the Army returned rounds and an un-involved English holidaymaker, Michael Hudson, died in the crossfire. The attack came the same day as another in which Lord Mountbatten died in a boat off the coast of Co Sligo, targeted by the IRA.
A republican splinter group, the Irish National Liberation Army, killed 17 people at the Droppin Well pub, Ballykelly, Co Londonderry. The dead included 11 soldiers based in the garrison town. An Army officer who rushed to the scene spoke of seeing bodies stacked like dominoes on top of each other.
The SAS ambushed and killed eight IRA men as they attempted to blow up a part-time police station at Loughgall, Co Armagh. The IRA raked the barracks with gunfire and used a digger to carry a bomb which they intended to destroy the site. The SAS fired at least 600 shots in response and all the dead republicans were shot in the head.
The SAS killed three IRA members in Gibraltar in March and were criticised because those they shot were unarmed. The funeral of the victims was attacked in Milltown cemetery in west Belfast by loyalist gunman Michael Stone, who killed three more. When two soldiers drove into the funeral of one of his victims, they were attacked by the crowd, beaten and shot dead.
Senior Metropolitan police commander Sir John Stevens headed up a probe into collusion between members of the security forces in Northern Ireland and loyalists following concerns about the shooting dead of Belfast solicitor Pat Finucane and other sectarian murders.
In October, two IRA bombs exploded inside the Army's headquarters in Lisburn, Co Down, killing one soldier.
Lance Bombardier Stephen Restorick, 23, was killed while manning a checkpoint at Bessbrook, south Armagh, in February. He was the last soldier to die in the conflict, shot by IRA sniper Bernard McGinn.
In April, Sir John submitted his report finding that members of the Army and police colluded with the Ulster Defence Association. The Army's Force Research Unit was linked to agent handling.
In August, former Northern Ireland secretary Peter Hain announced a two-year demilitarisation programme following the IRA's decision to stand down. The Royal Irish Regiment's Northern Ireland-based units were to be disbanded and thousands of members to be made redundant.
Troop levels were to fall to 5,000, leaving a peacetime garrison available for service around the world. Later that year, the first watchtower, Cloghogue - close to the border with the Irish Republic, was demolished.
In July, the Army's last south Armagh stronghold, at Bessbrook, was closed and Army chiefs confirmed Operation Banner would end on July 31.
Two sappers in the 38 Engineer Regiment - Mark Quinsey and Patrick Azimkar - were murdered by dissident republican gunman from the Real IRA outside Massereene Army barracks in Co Antrim. The soldiers, who were hours from deploying to Afghanistan, were targeted when they stepped outside the gates of the base to collect a pizza delivery.