Yanis Iliopoulos and son Alexandros discuss the referendum at home. (Luca Quagliato/For The Washington Post)

Yiannis Iliopoulos and his daughter fought so openly about how to vote in Greece’s monumental referendum Sunday that he wrote a public testament to say they were still on speaking terms.

Iliopoulos was dozing in front of the TV when Greek Prime Minister Alexis Tsipras broke into the broadcast just after midnight a little over a week ago to call a snap up-or-down vote on E.U. austerity demands. The out-of-work businessman threw on his clothes and made a late-night bank run, convinced he would lose his money if the nation voted down the bailout, as it did decisively on Sunday. But even as he stood in the ATM line to protect his cash, his daughter was making up her mind to reject five years of painful austerity that she said has crushed Greece’s economy.

In just a few short days, Greece has split into two polarized camps amid bitter arguments about its future in Europe. And some divisions have gone straight down the middle of families such as Iliopoulos’s. He and his daughter sniped about it all week on Facebook. His undecided son was caught in the crossfire.

“It’s not just the old disagreements inside society,” said Iliopoulos, 55, after casting his ballot Sunday. “It’s brought up a lot more anger and hatred” among various groups. He said he still loves his daughter even though he disagrees with her.

One part of Greece believes that the economic austerity demanded by E.U. leaders is the only way to guarantee the country’s place in Europe. The other has demanded an end to the cuts, saying that E.U. lenders have been treating the cradle of democracy with callous disregard.

In the end, Greeks turned out en masse to reject Europe’s tough terms, in a mark of their disgust with a half-decade of economic pain that brought them meager hopes for the future.

Now Greece’s leftist leaders must find a way to not only revive a banking system that sputtered to a stop this week, but also to unite a population that has turned on itself.

With European leaders holding a tough line Sunday, Tsipras and his team will struggle to keep Greece’s ATMs filled with cash in the coming days, a likely letdown for those who voted against austerity in the belief that banks would immediately reopen. But the true toll of Greece’s divisions will take months or even years to become apparent, with many here recalling the social splits at the time of the seven-year military dictatorship that fell in 1974.

The fighting and the anxiety have given Iliopoulos’s daughter Marianna, 28, a splitting headache for the past three days, she said, as she endured nonstop talk at her job at a publishing house — her first stable employment after years of looking, she said.

“I want something to change, because all these years we’ve been paying for austerity,” she said. As she posted a stream of anti-austerity status updates on her Facebook wall this week, her father started taking sharp exception in the comments sections.

“My friends started to ask, ‘What’s wrong? Why is he being so aggressive?’ ” she said. “Some of my friends asked, ‘Who is this guy? Is he your father?’ “

Aiming to defuse the tensions,Iliopoulos took to Facebook a day before the vote.

“I want to make it clear: with my daughter Marianna and with my son Alex, we don't have any personal differences. We just don’t share the same opinions,” he wrote.

Greek citizens lived through eight days of brinksmanship after Tsipras shocked the world by announcing the referendum.

The decision infuriated E.U. leaders, who abandoned negotiations and allowed Greece’s bailout to expire. It forced Greek leaders to shutter banks to avoid their total collapse. And life in this struggling Mediterranean nation came to a standstill as citizens talked about little but the referendum from morning till night.

Chatter around office coolers turned toxic. Butchers argued across the aisles in the venerable central meat market in Athens. Old friends blocked each other on social media. Many people in the “no” camp accused “yes” advocates of being traitors to their nation. Those who voted yes, meanwhile, said that the noes had been sold a fairy tale by their leaders that they could thumb their noses at Europe and expect concessions in return.

“People don’t talk about anything else these days,” said Alex Iliopoulos, 26, Marianna’s brother, who was deeply split between the camps and ultimately turned in a spoiled ballot to protest the entire idea of the referendum.

“Sooner or later, whether we are talking about our love life, our jobs, things turn political,” he said. “If everybody agrees, then it’s great. But if people disagree, then it can get nasty very quickly.”

Yiannis Iliopoulos said that he, too, thought that Europe’s austerity measures had done damage to Greece’s economy. Before the bailout, he was scraping by on his deceased wife’s pension, which averaged $835 a month. Now it has been cut by a third, even as taxes, power bills and medical costs have skyrocketed. His 90-year-old father recently moved in with him so that they could rent out the father’s home. Alex Iliopoulos, too, moved back into his childhood bedroom to cut his bills as he studies for a master’s degree in history.

But a no vote would be worse than austerity, Yiannis Iliopoulos said, because it would jeopardize the basis of Greece’s economy.

The gibes between father and daughter started midweek.

“I don’t care what people over 45 are saying, because we are the future of this country. And if we won’t manage it now, we will manage it in a few years. Sunday is coming,” Marianna wrote.

“You are supported by people over 45. They are your bosses, your friends or your families. This is the way Greek society works, for better or worse,” her father responded.

As they sat at an outdoor cafe near their polling station Sunday, the argument rekindled. Yiannis Iliopoulos told his daughter that her vote risked Greece’s membership in the euro zone, a privilege that he said had sparked years of prosperity and development in a nation that sorely needed it.

But before the euro, she replied, “you didn’t have people eating out of the garbage cans. You didn’t have them living under bridges. Now you see someone eating garbage and you walk right by, because it’s as normal as our having coffee right now.”

After the landslide results of the vote started coming in Sunday night, Iliopoulos was philosophical but fearful.

“I hope it’s not disastrous,” he said. “So the people voted. We have a democracy. We will follow what people voted.”

He paused.

“Tomorrow, we can talk,” he said.

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