The Irish backstop, a portion of the agreement for Britain’s planned withdrawal from the European Union, has been a near constant point of tension since the country began the Brexit process.

But the two players most affected by the potential outcome of this particular element of the exit — Ireland, an independent nation that will remain a part of the European Union after Britain’s exit; and Northern Ireland, a region that is part of the United Kingdom and is set to leave the bloc — often get left out of the conversation.

So what do Ireland and Northern Ireland want as Britain heads toward the next Brexit deadline? And can both be satisfied?

What is the backstop and why is it a factor?

Ireland and Northern Ireland have recently enjoyed cooperation across their shared border, which for decades had been a pressure point in sectarian struggles known as “The Troubles.”