By Dave Howard
Newsbeat politics reporter
Thousands of people in Northern Ireland have protested at the recent violence
These days, there's a whole generation of people who don't really remember serious violence in Northern Ireland.
To some people, it can feel more like a history lesson than real life.
There was concern that the killings of two soldiers and a policeman in March could re-ignite a bitter and bloody conflict that goes back decades - and is rooted in centuries of resentment.
Tension in the province seemed to calm over the next few months but rose again in July at the beginning of the annual marching season.
Twenty-one police officers were injured in violence in Belfast after rioting broke out in the north of the city before a parade was set to pass through.
British involvement in Ireland goes way back - to the 12th century, when an English king invaded with an army.
Five hundred years later, there was another big invasion - which led to decades of intense negotiation and bitter fighting.
The English repeatedly quashed Irish attempts to get back their independence.
'Patrick' Azimkar and Mark Quinsey were shot dead in March
In the 1920s it turned into another war.
The Irish Republican Army (IRA) were effectively fighting against their British rulers for independence.
Ireland ended up getting split into two parts.
It became British-run Northern Ireland as we know it, and a separate independent Irish state that we now call the Republic.
In the late 1960s, decades of unrest in Northern Ireland bubbled over and fighting flared up again.
Just like nowadays, there was a sizeable minority of Roman Catholics living there.
But they held almost no political power. So they began to protest.
It led to rioting and violence. Armed groups were formed to fight back against the IRA.
They saw themselves as loyal to Britain - so they were called "loyalist" fighters.
An IRA bomb killed five people at a Brighton hotel in 1984
British troops were sent to Ireland to keep the peace. But they were seen as yet more invaders, so they quickly got drawn into the conflict.
The Catholic population were angry because they thought history was repeating itself.
After that, there were 30 years of vicious bursts of fighting between the IRA and the British army.
It affected the rest of the UK, with bombings on the British mainland, and loyalist groups would often retaliate whenever there were IRA attacks.
Perhaps the best known violent episode came on 30 January 1972 - when British soldiers opened fire on a civil rights march.
Fourteen people ended up dead and it became known as "Bloody Sunday".
In 1984 an IRA bomb went off at a hotel in Brighton.
The Conservative Party conference was going on at the time and many top politicians, including the then Prime Minister, were staying in the hotel.
PM Margaret Thatcher narrowly escaped but five people were killed
In total, during this whole period, over 3,000 people died.
Good Friday Agreement
It's difficult to pick a point when Northern Irish peace started to be achieved.
But if you had to choose, it might be 10 April 1998.
Politicians from all sides got together to sign a document setting out how Ireland, Northern Ireland and Britain would deal with each other. It was called The Good Friday Agreement.
There were so many bitter arguments that people thought it was a miracle there was any agreement at all.
The Good Friday agreement freed prisoners on both sides
It meant that armed groups like the IRA and the loyalist fighters were supposed to put down their weapons.
Prisoners from those groups were also meant to be released from jail.
There were fears that the police force in Northern Ireland - called the RUC - was unfair to the country's Catholic community, and there were calls for it to be changed.
It also meant politicians from all sides of the argument were elected to sit in the Northern Ireland Assembly.
It was seen as a massive step forward - even though a series of problems meant the Assembly's powers were repeatedly taken away.
As the months and years have worn on, the gaps between the violence have seemed longer and people have become more optimistic about a lasting peace.