With more than 3,600 dead and around 50,000 injured, the conflict in Northern Ireland, commonly referred to as The Troubles, was one of the bloodiest civil wars in recent European history. It officially ended 20 years ago on April 10, 1998, with the signing of the Good Friday Agreement in Belfast. Predominantly Catholic republicans, who were pushing for reunification with Ireland, and largely Protestant unionists, who viewed Northern Ireland as a legitimate part of the United Kingdom, reached out their hands and agreed to peace for the first time.

The Irish Republican Army (IRA), which, depending on one's views, could be seen either as a terrorist group or as freedom fighters, agreed to disarm at the time. Republicans and unionists then built a joint regional government that has since collapsed several times -- most recently in 2017. There are still armed groups on both sides today seeking to torpedo the peace process.

Gerry Adams, 69, was one of the architects of the Good Friday Agreement. He headed the Sinn Féin political party, which was considered the political arm of the IRA. Adams still represents the party in the Irish parliament in Dublin. British authorities continue to maintain that he was a commander in the IRA, a claim which Adams denies.

DER SPIEGEL: Mr. Adams, 20 years after the Good Friday Agreement, republican and unionist parties are fiercely divided, and violence is increasing on Northern Irish streets. Is that what peace looks like in Northern Ireland?

Adams: I wouldn't exaggerate the situation. There's probably more violence in any German city at this time than there is in the north.

DER SPIEGEL: Paramilitary-style acts of revenge in Germany are very rare. In Northern Ireland, however, they have increased by 60 percent in the last four years.

Adams: That's residual. There are small, non-representative groups. They don't have any real capacity. They certainly don't have any popular support. The IRA had a great deal of popular support when it was in its ascendency and the capacity to conduct a war against the British. Thankfully, that's over. The IRA is gone.

DER SPIEGEL: A group is involved in the current conflict that calls itself the "New IRA." Who are they?

Adams: I'm not here to explain any of these groups. I think most of them are criminals without any political support. There is now a democratic way, a popular, peaceful way to bring about Irish unity.

DER SPIEGEL: But there are clearly still a lot of weapons around in the north. And now Brexit is coming. Does it have the potential to torpedo the whole peace process?

Adams: The British government conducted a referendum on Brexit totally ignoring, perhaps oblivious to, the damage it would do to Ireland. The north voted against Brexit. If the English Tories have their way, there will be a hard economic border. That's going to be totally and absolutely disastrous.

DER SPIEGEL: Would that bring back the violence?

Adams: Your questions suggest that there is a volcano ready to explode. No. The vast, vast majority of people value the peace process. It is in my opinion not under threat. And the way to go forward in the first instance about Brexit is for designated special status for the north. It's to keep the north within the European Union to avoid economic hardships.

DER SPIEGEL: That would infuriate the Northern Irish unionists upon whose support Prime Minister Theresa May's minority government depends. And a hard border between the north and the south would be intolerable for the republicans. It's a Catch 22.

Adams: More important than the republicans or the loyalists is that if the economy is fractured, the ordinary folks are the ones who are going to suffer. In the north and in the south. It won't affect Theresa May.

DER SPIEGEL: Many people in Northern Ireland say that even the smallest customs hut at the border will be attacked. To protect it, there would be police, which would creat even more targets. It could spiral into a vicious circle.

Adams: Of course, it would be a provocation and there are always dangers. But as someone who has survived 30 years of fighting, I can assure you there will be no return to the past. All that's done. That's over. It's finished with.

DER SPIEGEL: You were 17 when you joined the fight. Why?

Adams: I came from a very poor, working-class neighborhood in Belfast. We had no inside toilet. We had no hot water. We had a water tap in the yard at the back of the house. And that was common for people from that background. I ended up going to a grammar school in West Belfast. And in 1964, on my way to school, I witnessed the state police attacking an election office. There was a general election. Sinn Féin was banned. It was outlawed. Newspapers were banned, emblems, symbols, recordings. The Irish national flag was actually also outlawed. I went down to the government publishing office and bought a copy of the Special Powers Act, just out of curiosity. And I read what the British state was entitled to do on our island. And then I had some explanation for the poverty in which people like us were living. So, I joined Sinn Féin. That's my sort of course into republican and other activities.

DER SPIEGEL: You also fought on the street. Did you ever shoot at people?

Adams: No.

DER SPIEGEL: Is violence a legitimate means with which to reach one's aims?

Adams: I think in given circumstances. And the circumstances at that time in the north were that people were being denied their rights. The English occupiers refused to concede those and in fact attacked the demonstrators. The most disastrous mistake that the English government made is that they handed the situation over to the generals. That always leads to a militarization of the situation. Military people are not there to pacify, they are there to subjugate.

DER SPIEGEL: The IRA wasn't there to pacify either.

Adams: The people that I know didn't go to war. The war came to us. I woke up one morning, and the British Army were in occupation of the local school, the local football pitch, the local social center, the roadblocks were up. They were stopping you. They were throwing you up against the wall. They were arresting you. They were molesting women, and so on and so on.

DER SPIEGEL: You have defended IRA violence on multiple occasions as "legitimate resistance." As a devout Catholic, how do you reconcile that with your faith?

Adams: It's still my view that the use of armed actions in the given circumstances is a legitimate response. Whether you exercise that right is another issue. And of course, there were many things that the IRA did which were wrong. And I both condemned at the time and deplore and regret it to this time.

DER SPIEGEL: Was there a single defining moment for you that convinced you to search for a peaceful solution?

Adams: I would argue that I always wanted peace. Remember, I was politically active before the conflict started.

DER SPIEGEL: The republican movement considered every concession to be a form of betrayal. What made you so sure you wouldn't wind up with a bullet in your head when you began pushing for peace with the archenemy?

Adams: First, it was not only me. Within Sinn Féin, we decided as a group that we wanted to reach out to our unionist neighbors. We weren't going to get the type of republic we wanted unless Sinn Féin became a political party that could be in the vanguard of bringing that about. Of course, it was risky. But look, and I don't want to be sounding blasé about this, there already would've been a long queue of people trying to shoot people like me.

DER SPIEGEL: Was it tougher to convince the hardliners within your own ranks or the side of your opponents?

Adams: The hardest negotiation is always with your own side.

DER SPIEGEL: By the time you finally reached the Good Friday Agreement in 1998, more than 3,500 people were dead. Was it worth it?

Adams: Well, it's hard to measure it in those ways. Of course, it would've been far better if not one person was killed or injured. But you don't pursue and you don't get progress without struggle. And I say that as someone who has lost a lot of family members and friends and who has been tortured and shot myself. I've been there, and I've been at many, many funerals. But of course, you can only measure all of this at the end of all of this. And I do believe that Irish unity is going to be the reality.

DER SPIEGEL: But hundreds of innocent civilians were killed for that cause.

Adams: Many armed groups were involved in the conflict. Regardless of who was responsible, I regret all the dead. Our cause and our commitment must be to ensure it never happens again.

DER SPIEGEL: Have you ever forgiven your enemies?

Adams: Yes. I learned a long time ago the only person who will suffer from hatred is yourself. I negotiated for the release of loyalist prisoners, the guys that shot me. Obviously, they were dreadfully bad shots. And in fairness to them, they were doing what they thought was right.

DER SPIEGEL: And could your enemies ever forgive you?

Adams: You can't generalize like that. There are still people out there who detest either the British or the unionists or the IRA or whoever the other protagonists were. But you can't make that an obstacle to going forward.

DER SPIEGEL: If you look at Northern Ireland now, Catholics and Protestants are even more segregated than they were. They send their kids to different schools, they bury their dead in different graveyards.

Adams: You are right, the issue of sectarianism and the issue of a segregated society is very disappointing. At the same time, the 12th of July, which was always a sort of most troublesome part of the year, has been relatively peaceful for the last number of years. Issues around (the Protestant) Orange Order marches coming into (Catholic) communities which didn't want them -- that has mostly been sorted.

DER SPIEGEL: But it still feels like people in Northern Ireland are walking on very thin ice.

Adams: You can't undo history in a few years. In the north, it was always about people fighting for their rights and others trying to hold them down. And it still is. That may sound a bit odd in the year 2018, but that's the reality of it.

DER SPIEGEL: Was it a mistake that there was never a truth commission modeled after the one in South Africa?

Adams: Sinn Féin wants a truth commission, an independent international truth recovery process. The British government doesn't.

DER SPIEGEL: In a united Ireland, unionists would be in the minority in the future. Do you really think that would settle the conflict for good?

Adams: It depends on what sort of united Ireland we will have. We need one that is agreed upon by the people and that underpins the rights of everyone. All the unionist parties have not signed up for the general position that, if the people democratically vote for a united Ireland, they have to accept that. So, we have a big job to do. Do we have the ability to create an Ireland in which people are treated equally? Yes, we do.

DER SPIEGEL: Let's assume there will be a vote. And let's assume there will be a 52 to 48 percent outcome for unification. What happens then?

Adams: The way democracy works in most societies is that you vote, and whoever gets the most votes wins, right? That is what was agreed in the Good Friday Agreement. But in terms of both a sustainable and stable transition from the current situation to a new Ireland, we're quite open to that being done in a phased way. To a certain degree, it has to move at the pace of the slowest passenger. Everyone needs ownership of the future.

DER SPIEGEL: Could Brexit open the door for a united Ireland?

Adams: Brexit is such a disaster that I don't want to leave myself open to even an accusation of exploiting it. So, I would go no further than to say that it has alerted people who wouldn't be united Irelanders to the awful consequences if we saw a hard border on the island of Ireland. Now there's cooperation on health, on energy and agriculture, on industry and enterprise and waterworks. There's so much happening across the island, and it's all to the mutual benefit of everybody on the island. So, most people would be alert to the disaster. And nobody knows how this is going to turn out.

DER SPIEGEL: Sinn Féin has seven elected members of parliament in Northern Ireland who could move into the House of Commons in London but have refused out of tradition. Why doesn't the party abandon this position to change the game in British politics?

Adams: First, it wouldn't change the game numerically. But the main reason that we won't do that is because we're not mandated to do that. The people had a choice. They could've voted for a range of other parties. What they've done is basically turned their backs on Westminster.