The Irish backstop, part of the UK's planned withdrawal from the European Union, has been an almost constant tension since the country began the Brexit process.
But the two players most affected by the potential outcome of this particular element of the end – Ireland, an independent nation that will remain 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 block – often gets out of the conversation.
So what does Ireland and Northern Ireland want when Britain heads for the next Brexit deadline? And can both be satisfied?
What is backstop and why is it a factor?
Ireland and Northern Ireland recently enjoyed cooperation across their common border, which for decades had been a press point in sectarian fighting known as the "Problems." Republicans, usually Roman Catholics, who believed that the six counties in the north should be part of a united Ireland; and historically dominant unionists, largely Protestants who wanted Northern Ireland to remain part of the United Kingdom.
In the years since the peace agreement, the common economy of the EU gave room for free trade and easy movement across a border is now almost invisible.
Backstop is a set of temporary measures that would be introduced until Britain and the EU reached a long-term trade agreement that would eliminate the need for a physical border.  Under these measures, Britain would remain in the European Customs Union (not charging European products tariffs) and Northern Ireland would follow many rules in the single market (eg obey many European product and food standards.)
For Unionists, that is almost an existential threat, because the measures will bind Northern Ireland more closely to European rules than they would the rest of the United Kingdom they fear would lead to ultimately
What does Ireland want?
Leo Varadkar, Ireland's Taoiseach, as Prime Minister known, has said that backstop is an essential part of any repurchase agreement.
On Tuesday, Mr Varadkar told reporters in Paris that no scenario would put Ireland in a "difficult situation". He reiterated his long-standing claim that his country's twin objective was to protect the peace agreement and protect the integrity of the internal market and the customs union. The best way to do that, he said, was with the current backstop agreement.
They are the foundation "where Ireland's economic model, our job and prosperity have been based for many decades now," said Mr Varadkar. 19659015] What does Northern Ireland want?
Members of the Democratic Unionist Party or the DUP oppose any language of the Brexit Agreement, which proposes a particular status for Northern Ireland, claiming that the term could threaten to break up in the United Kingdom.
But the goals for Northern Ireland as a whole are a little more opaque, more complicated by the fact that the region has been without government for two years. While Northern Ireland is part of the United Kingdom, it has its own legislature in Stormont, Belfast.
As a result of the same peace agreement that conveyed peace in Northern Ireland, the government must be a two-party power-sharing coordination. But two years ago, there was a disagreement between the two governing parties at that time – D.U.P. and the Republican Sinn Fein party led to the government's dissolution in Stormont.
A new government has not yet formed. While D.U.P. has been able to exert influence in London as part of Prime Minister Theresa May's governing coalition, the broader interests of the region have not always been represented.
Sinn Fein lawmakers who refuse to sit in the British Parliament now worry that an unapproved Brexit would mean that Northern Ireland's decisions end up being completed in London by the return of the "direct rule" which the peace agreement should end. Britain's top official on Tuesday indicated that it was an option that took ire from Sinn Fein.
Complicating cases are that a majority of Northern Ireland voters – 55.8 percent – voted to remain in the EU.
Can There be compromise?
It doesn't look likely.
Sammy Wilson, a DUP member of the MP, recently said that although Mrs May brought back his deal 1,000 times, " we will vote against it." "He demanded that the Prime Minister" only signed an agreement that deals with Northern Ireland the same as the rest of the United Kingdom. "
Senior members of Mrs Mays Conservative Party are said to be dangling something called a" & # 39; Stormont Lock & # 39; & # 39; to win the support of unionists. saying that if Northern Ireland had to adapt its rules to comply with European standards, it would also be the rest of the United Kingdom.
But Unionist leaders were unconvinced, warning that an international treaty with one the backstop – the Brexit Agreement – would take precedence over domestic measures that attempt to avoid one.