Hundreds of ex-Army personnel and the Royal Irish Regiment have attended a parade to remember the start of Operation Banner.
The parade took place in Lisburn and veterans laid wreaths at three memorials.
The event marked the 50th anniversary of troops being deployed in Northern Ireland in August 1969 in what the Army refers to as Operation Banner.
Operation Banner lasted until 2007, costing the Army hundreds of lives.
It became the longest continuous campaign in British military history.
As part of the commemoration event, an Ulster Aviation Society Westland Scout Helicopter and old military vehicles were displayed outside the Irish Linen Centre and Lisburn Museum.
Ian Simpson, of the Northern Ireland Veterans’ Association, which hosted the event, said: “This 50th Anniversary of Operation Banner is a milestone in the history of Northern Ireland and we are honoured to hold this landmark event in Lisburn.”
He said it was a chance to remember those who died or were injured in the Troubles.
Mayor of Lisburn and Castlereagh City Council Alan Givan said: “Being a garrison city, it is fitting that Lisburn has been chosen by the Northern Ireland Veterans’ Association as the location to remember and commemorate those service men and women who tragically lost their lives and the many who were injured during this period. “
‘Kept NI going’
Speaking at the event, DUP leader Arlene Foster said it was “important to remember those who served through that time”.
“Those people who are here today stood between us and anarchy actually, during the 70s, 80s and 90s,” she said.
“Therefore we are very grateful.”
Her party colleague, MP Sir Jeffrey Donaldson, who served in the Ulster Defence Regiment (UDR) said the parade was about “honouring the sacrifice of those who stood on the front line”.
“They helped to keep Northern Ireland going at a time when we had a lot of trouble in this place,” he said.
“And they helped to create the space in which today, we enjoy a relative degree of peace.”
Jason Olding, who served with the 1st Battalion Royal Green Jackets, had not visited Northern Ireland since his time in the Army, almost 30 years ago.
“You were always aware of the dangers,” he said.
“You know that every second could have been your last, but we did our job as professionally as we could and tried not to think too much about it.
“Being here is very emotional – a lot has changed. People aren’t as hostile as they were before.”
The Ministry of Defence said 722 soldiers were killed in the Troubles as a result of “hostile action”.
Deaths attributed to the Army number 297, according to Ulster University’s conflict archive. These include killings in controversial circumstances.
From the first deployment in August 1969, troop numbers swelled considerably over the years, peaking at 27,000.