When I first started covering conflict zones many years ago, I resolved never to bother with the Troubles in Northern Ireland.

I had grown up in Boston, where every bar in Irish neighborhoods had a box for donations to the Irish Republican Army (IRA). The IRA was then fighting with bullets and bombs to remove the six counties on the northeast part of the island of Ireland from their union with Britain and unify them with the Republic of Ireland to the south. I considered the war between Northern Irish Protestant unionists who wanted to stay with Britain and the Catholic nationalists to be hopeless. (Instead, I focused for decades on the Israeli-Palestinian struggle, which proved to be never-ending.)

To the world’s, and my, surprise, the 1998 Good Friday Agreement mostly ended the conflict within Northern Ireland. That accord — brokered with U.S. help — produced one of the few (maybe the only) happy ending to the kind of brutal civil wars that are becoming the new normal in an increasingly nationalist world.

So it is disgusting to see British Prime Minister Boris Johnson threaten the future of the agreement, and carelessly provoke renewed violence in Northern Ireland. The moves of Trump-clone Johnson over Ireland display the dangers posed by self-centered populist nationalist leaders who put their own political survival above the well-being of the countries they lead.

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What eased the resolution of the Irish conflict was the fact that Britain and the Republic of Ireland were both members of the European Union (EU). Irish Catholic nationalist leaders could assure their followers that, under the Good Friday Agreement, the border between Northern Ireland and the republic would be fully open for the movement of trade and people. Because they were both part of a larger alliance — the European Union — the border between the north and south of Ireland became almost invisible physically, with no customs checks or guards between them.

“The pressure was eased when Northern Ireland became part of a bigger whole,” I was told by Katy Hayward, professor of political sociology at Queen’s University, Belfast.

Then came Brexit, when Johnson pulled Britain and Northern Ireland out of the European Union, feeding Brits a host of false facts about the benefits they would gain. The Republic of Ireland remained an EU member. That meant Brexit raised the prospect of renewed checks at the border between the republic and the north, which would violate the basics of the Good Friday Agreement.

“You can’t underestimate the significance of Brexit for changing the relationship Northern Ireland had with the rest of the United Kingdom and with the republic,” Hayward says. “That’s why we see such tensions at the moment.”

The EU, not wanting a renewed civil war, demanded that the internal Irish border stay open as a part of its trade deal with post-Brexit Britain. At first, Johnson agreed to a technical workaround, putting a customs border through the Irish Sea between Britain and Northern Ireland. But this angered Northern Ireland’s hardline Protestants because it seems to separate Northern Ireland from Britain.

Protestant demonstrations and bus burnings began again.

Yet, instead of working out a deal with the EU to calm things down, Johnson is fueling the unrest, threatening to abrogate his agreement with the EU on the Irish border. Picking a fight with the “enemy” EU works to stir up his base, and the British leader needs that support because he is under pressure from a COVID-19 resurgence and a scandal within his Conservative Party.

“The British government has inflamed unionist opinion on this [the Irish Sea customs border], which is so dangerous,” says Philadelphia Cong. Brendan Boyle, who has focused on this issue. “Once you whip up hysteria among the unionist community, it is hard to tone it down.”

What’s so tragic about Johnson’s demagoguery is that it reverses the truth. Northern Ireland benefits from its dual customs status — which gives it free access to European as well as British markets. Moreover, the EU has already eased customs requirements for exports across the Irish Sea.

It is Johnson who has refused to help ease genuine Protestant business and political concerns.

Hopefully, Johnson will recognize the risks he faces in fomenting another Irish civil war before it is too late.

President Joe Biden and Congress have made clear the firm, bipartisan U.S. stand against undermining the Good Friday Agreement (which was godfathered by negotiator and former U.S. senator George Mitchell, and supported by GOP and Democratic presidents alike).

Ireland’s ambassador to the United States, Daniel Mulhall, notes that the Irish taoiseach (prime minister) Micheál Martin recently said a move by the British government to trigger Article 16 — which would suspend the EU-U.K. agreement on the Irish border — would be “reckless and irresponsible. It could undermine the entire EU-U.K. trade agreement and create a lot of tension between Ireland and the U.K.”

Should he be so foolish as to push Northern Ireland back toward the Troubles, Johnson will go down in history as the man who managed to wreck the Holy Grail of peaceful civil war endings - in pursuit of an English nationalism that has brought more harm than gains.