It was supposed to be a short deployment.
By Vincent Kearney
NI Home affairs correspondent
The thousands of British troops who arrived on the streets of Northern Ireland in August 1969 had no idea what lay ahead.
"We thought we'd be home by Christmas," recalls retired Lt Colonel Mike Jelf, who led a platoon of the Queen's Regiment onto the Falls Road on 15 August.
He had been part of the peacetime garrison based at Palace Barracks in Holywood, County Down, as Northern Ireland descended into chaos.
"It was a great place to be," he said. "It was a fishing, hunting and socialising posting."
But that all changed in August 1969.
The police could not cope after three days of rioting in Londonderry, in what became known as the Battle of the Bogside, as nationalists rebelled at what they saw as a unionist militia, not an impartial police service.
There was also mayhem in Belfast as sectarian clashes led to thousands of people being forced to flee their homes.
On 14 August, the troops arrived on the streets of the Bogside, and the following day they marched into Belfast.
Mike Jelf was among the first to be deployed, leading his troops along Percy Street, which linked the loyalist Shankill and the nationalist Falls roads.
"It was our first experience of what was essentially a war zone.
"We couldn't believe what we saw. Houses had been reduced to piles of rubble, there were burning vehicles across the road. I will never forget the smelling of burning, it was everywhere," he said.
"The Catholics were delighted to see us. It wasn't long before tea and food was brought out, in fact there was so much that after a while we simply couldn't take any more."
But the honeymoon period didn't last long. Before long, many nationalists viewed the Army as the enemy.
Thousands of troops arrived on the streets of Northern Ireland
For many, the turning point came in July 1970 when huge numbers of troops moved in to search Catholic homes, with the residents ordered to remain indoors, in what became known as the Falls Road curfew.
Retired Lt Colonel Jack Daw was with Mike Jelf when they were welcomed onto the Falls less than a year earlier, but this time it was very different.
"There was a very marked change in attitude. We were quite aggressive as we were under orders to search every house, alleyway and drain in the area and we found a lot of weapons," he recalls.
"But it was clear that the Catholics didn't want us there anymore. There were no more cups of tea, we were the enemy."
That perception was reinforced by the policy of internment in August 1971 when 3,000 soldiers took part in a series of raids to arrest alleged terrorist suspects.
More than 300 Catholics were arrested, many of them innocent. No loyalists were detained.
Any lingering nationalist goodwill towards the Army finally evaporated when soldiers killed 14 civilians in Londonderry in January 1972, in what became known as Bloody Sunday.
As the IRA grew stronger and violence escalated, the Army became embroiled in what became known as Operation Banner - the military support role for the police during the Troubles.
There were many areas where it was simply too dangerous for the police to operate on their own.
Percy Street linked the loyalist Shankill and the nationalist Falls roads
More than 300,000 soldiers served in Northern Ireland during the Troubles, in what was the longest continuous campaign in British military history.
Seven hundred and sixty three military personnel were killed, and soldiers killed 301 people, more than half of them civilians.
At the height of the Troubles in 1972 there were about 27,000 military personnel on the streets of Northern Ireland.
To put that in context, 26,000 British soldiers were deployed for the invasion of Iraq in 2003, and today the combined total of British servicemen in Iraq and Afghanistan is 12,400.
At midnight, Operation Banner will finally come to an end, 38 years after the first troops arrived.
From Wednesday, the peacetime garrison will be no more than 5,000 troops, around the same as it was before the troubles began.
And the role of those soldiers who remain will be very different - they will be available for deployment in trouble spots across the world, not on the streets of Northern Ireland.
That chapter of the Army's history is over.