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.”