The events mark King William of Orange’s victory over James II at the Battle of the Boyne in Ireland in 1690.
Huge Eleventh Night bonfires ushered in the biggest date in the Orange Order’s calendar.
Firefighters dealt with 40 bonfire-related incidents — up 21% on last year — and received 213 emergency calls, and mobilised to 133 incidents overall — a 49% hike on 2016.
The Northern Ireland Fire and Rescue Service (NIFRS) described the night as “exceptionally busy”, with crews dealing with 95 operational incidents between 10pm and 1am. During the most intense period, the NIFRS’s regional control centre handled an emergency call every minute.
Homes were boarded up at a number of bonfire sites amid concerns around safety and risk to property.
Firefighters doused at-risk buildings with water in an effort to keep them cool as the fires raged nearby.
The NIFRS said its two most significant bonfire incidents were in the greater Belfast area. The service also reported one attack on a fire appliance during the night — though no one was injured.
Sinn Féin reacted angrily to a coffin bearing an image of the late Martin McGuinness being attached to one bonfire in east Belfast, while Irish Tricolors and posters of Sinn Féin and other non-unionist politicians were a common sight on many fires.
However, a peaceful Orange Order parade past the Ardoyne flashpoint in Northern Ireland was described as a massive step forward by a community worker.
The north Belfast trouble spot had become a byword for conflict over many years on the Twelfth of July, but a deal struck between local residents saw a “relaxed” early-morning demonstration replace a tightly restricted evening procession where violence always threatened.
Loyalist bandsmen from nearby Shankill and Ballysillan banged the Lambeg drum on the arterial Crumlin Road, followed by lines of white-shirted men wearing the Order’s collarette, while a handful of nationalist residents looked on.
Fr Gary Donegan, a Catholic priest who has spent years working in Ardoyne, said: “Every step that happens here, no matter how small, it is is massive.”
There was a heavy police presence, mainly confined to residential side streets off the Crumlin Road.
But officers trained for riots never left their vehicles, remaining spectators to the noisy pageantry with which unionists say celebrates their culture, but which nationalists blame for much strife in recent years.