In mid-January, a taciturn, chain-smoking Iraqi politician came to Washington to meet with powerful members of Congress, White House advisers and think-tankers and convey an urgent warning. Iraq is about to explode, he said, and the United States needs to pay attention.

He described a country poisoned by sectarianism, beset by a virulent Islamist insurgency and hampered by a divisive prime minister, Nouri al-Maliki, a Shiite Muslim who had marginalized the Sunni sect, creating dangerous resentments.

But the visitor, Saleh al-Mutlak, Iraq’s deputy prime minister and a rare Sunni officeholder, soon realized that in official Washington, Iraq was old news, settled business. Mutlak says his takeaway after a week of discussion with U.S. foreign-policy makers was, “Good luck, you’re on your own.”

Well surprise, surprise.

Iraq indeed did blow up this month, as a Sunni extremist group few Americans had heard of — the Islamic State of Iraq and Syria — overran the feckless Iraqi army, took control of key cities and claimed large portions of northern and western Iraq. Suddenly ISIS, the evil spawn of bloody conflicts in two besieged Arab states, became a crucial talking point even among people who didn’t know what they were talking about.

It was a rerun of a familiar Washington ritual as the political players lined up to posture. Who’s to blame? Why didn’t anybody see this coming?

You could ask the same question about the Russian takeover of Crimea, the Arab Spring, Saddam Hussein’s invasion of Kuwait in 1990, the Soviet occupation of Afghanistan in 1979.

Or the economic conflagration of 2007. Or the surprise defeat of House Majority Leader Eric Cantor (R-Va.).

Huh? How did this happen? Who knew?

In several of the above cases, many people did know. And leaders didn’t listen. The United States, for example, continued its embrace of Maliki, though the Obama administration is now reportedly looking for an alternative.

But in the great rush to opinion-mongering that follows Surprising Big News, something often is overlooked: The future is unwritten, and you really can’t see everything coming.

“The world is very complicated,” says Seth G. Jones, a Rand Corp. senior analyst and military adviser. That sounds utterly obvious, but he points to “the complicated nature of these events in Iraq” as a good example.

Members of Congress who served in Iraq reflect on the instability in the region, and weigh in on what's missing in the debate about U.S. involvement. (Theresa Poulson/The Washington Post)

“In social events like this, in warfare, it is very difficult to predict with any sense of certainty events unless you are right up against them, a few days before they happen,” Jones says. “The U.S. intelligence community and policy community more broadly were aware of serious concerns in Iraq — grievances among the Sunnis, sectarian fighting, a larger number of attacks by ISIS — but I don’t know that anyone predicted the timing, the severity of what unfolded.”

Not even Mutlak — who campaigned, unsuccessfully, for prime minister in the recent election — forecast any specific ISIS conquests when I spoke with him in Baghdad in April. His concerns broadly included sectarian civil war and the spread of violence beyond Fallujah and Ramadi in Anbar province, where ISIS, an al-Qaeda offshoot, and other militants were battling the Iraqi army.

Political scientist Jay Ulfelder says part of his work involves assessing the potential for coups, civil wars or state-led mass killings of civilians. “People are quick to say, ‘Nobody saw it coming,’ but if you go back and look, you will see that most people were not saying anything clear about what was happening. They use a lot of fudge words — ‘could have,’ ‘might be.’ ”

Barbara Slavin, a senior fellow at the Atlantic Council and former reporter in the Middle East, says some events that unfolded last week could have been obvious.

“But it’s always the same with the intelligence community,” she says. “They have no imagination.”

There also are times when trouble is looming but no one wants to see it; better put that one in the “too hard” box. Just can’t deal with it right now. Too much other stuff.

Blame belongs in part to “the attention deficit disorder of senior leaders,” says Derek Harvey, a former top U.S. military official in Iraq who used to brief such leaders. “They are busy people, they only have so much time, their inboxes are full, and they put on the list of priorities what is staring them in the face. Unless the analysts push the issue to the front and take some risks and say, ‘You need to focus on this,’ they won’t.”

Normal news consumers know the feeling. It’s like being pecked to death by chickens. Iranian nukes. Ukraine. What’s up with Putin? Pakistan. China. Afghanistan — we still there? Iraq — wait, that’s history.

“What policy leaders get are CNN headlines of the day,” says Harvey, “a PowerPoint slide, snippets, not an hour-and-a-half deep dive.”

Harvey served as an adviser to Gen. David H. Petraeus and has experience with Iraq stretching to the 1980s. He says Mosul was just a tree waiting to fall. “Nobody was connecting the dots,” he adds, using a very familiar phrase.

Flashback to Sept. 11, 2001. Years earlier, a bipartisan commission studied an array of threats to the United States, including weapons of mass destruction and terrorism. The Cassandras warned of an unspecified but inevitable and horrific attack on American soil. They called for creation of a homeland security agency to defend against coming attacks.

Their reports, and earlier ones, languished.

“We Americans have an ability to procrastinate until we get hit on the head by a 2-by-4,” the late senator Warren Rudman (R-N.H.), who co-chaired the commission, told me shortly after 9/11. Rudman was in a cab en route to his law office when he heard the news of the attacks on NPR. He thought to himself, “Oh, God, we predicted this.”

Political recriminations soon followed: Somebody should have known. Who was asleep at the switch? Who’s to blame?

Nicolle Wallace, a former George W. Bush White House communications director, says that partisanship can make it hard to accept that events can overtake our political perceptions. “That reflex to say, ‘Why didn’t they know?’ ” she says, “is an extension of the need to find a culprit for everything that happens.”

An exacerbating factor: Many people now follow world events through a partisan media prism. “It has made what in the past was breaking news seem like someone’s conspiracy,” she says. “It is an equal-opportunity weapon that each side uses on the other.”

Now playing out on the blogs and chat shows: Who lost Iraq? As its distant, sandy landscape rises again in our consciousness — remember Baqubah, Tal Afar, Samarra? — the think tanks and networks trot out quote dispensers with familiar names.

There’s retired Gen. Jack Keane on Fox News. There’s Danielle Pletka of the American Enterprise Institute. There’s Tony Blair.

Tony Blair!

“Iraq is now in mortal danger,” Britain’s former prime minister writes on his Web site. “The whole of the Middle East is under threat.”

He also writes, “The sectarianism of the Maliki government snuffed out what was a genuine opportunity to build a cohesive Iraq.”

It’s exactly what Mutlak was saying during his visit, in urging the Americans not to supply more Apache helicopters to Iraq without conditions for political reforms. But nobody cared.

On the Voice of America site last week, Slavin wrote of the latest events in Iraq, “Saddam Hussein must be laughing in his grave.”

Which really would come as no surprise.