In the first week of the second decade of the third millennium, it was 68 and sunny southeast of Baghdad. At an outpost known as Contingency Operating Station Hammer, intelligence analysts for the U.S. Army sat at workstations in “secure classified information facilities” and combed through “classified significant activity reports.” Beneath the jargon was a clearer snapshot of the dawn of the 2010s: bored and exhausted young Americans, sequestered in sun-blasted warehouses on a patchwork battlefield, scanning terse bulletins about the execution of civilian informants, about shrapnel in the Green Zone, about the cooking pots and jagged wires that were used to make “improvised explosive devices,” which itself was a euphemism for “bombs.”

Back home, on Jan. 5, 2010, President Barack Obama was fuming about security lapses that allowed an al-Qaeda terrorist to board a flight from Amsterdam to Detroit with a bomb sewn into his underwear. And at COS Hammer, an analyst from dirt-road Oklahoma was starting to download classified reports onto wiped CDs, one of which was labeled “Lady Gaga.” The pop phenom’s single “Bad Romance” was playing everywhere in the United States. The song was about one lover’s desire to know the darkest parts of another. Chelsea Manning, then a private first class, was using Gaga as a decoy.

Among Manning’s downloads were grainy aerial videos showing the slaughter of civilians, plus cables and reports that breezed away the fog of war. Manning would sort, compress, encrypt and upload the purloined files to WikiLeaks, which would then publish “The Iraq War Logs,” comprising 391,832 such reports. It would be the largest leak of national-security material in American history. The logs would detail and dramatize a disastrous war that many Americans had lost sight of. Over the following decade Manning would be convicted of espionage and watch from prison as people labeled her a hero, a criminal, a martyr. But on Jan. 5, 2010, Manning was just an unknown 22-year-old, serving in a forever war, believing that her private transgression was in the public interest.

“I want your everything as long as it’s free,” Gaga was singing.

Information belongs to the public, Manning would later type, in an anxious message to a friend. “I just . . . couldn’t let these things stay inside of the system . . . and inside of my head.”

Two months after Manning sent that message, a software engineer named Mike Krieger uploaded one of the first photos to a new social media platform that would soon be called Instagram. It depicted a blurry, tilted view of a marina through a windowpane, and it was very uninteresting. But it was the start of something, and would acquire meaning in retrospect. Before the decade was out, Instagram would be sold to Facebook for $1 billion. By 2018 it would have over 1 billion active monthly users: influencers and voyeurs, joined in algorithm, in a system, snooping through artificial versions of themselves, scrolling and touching-up and liking and yearning to be liked. Cults developed — not of personality, but of image and lifestyle. Software learned what we desired, then fed us more of it.

At first you could filter a photo, soften the edges, make life seem a little less ugly in the pursuit of validation. Then you could tune your actual face, make it smoother, younger, plumper. This year a 20-something Brit named Levi Jed Murphy got a lip lift, brow lift and canthoplasty to reshape his eyes so that he became a living filter.

“Getting surgery so i spend less time facetuning my pics which means less time on my phone which results in my battery lasting longer,” Murphy wrote below a photo of his bandaged nose and bruised eyes.

At the end of the decade, users are still finding and commenting on that early crude photo posted by Krieger, as if they were visiting a World Heritage site, or scrawling on the Parthenon. “Where it all started,” one user wrote recently, and the “like” button became “more important than air and water.”

You can measure time in prison terms or in presidential terms. You can divide it into light-years, generations, target-date retirement funds. You can estimate it using more abstract variables: followers, parts per million, unique views, gigabytes, gunshots, the thickness of sea ice. An easy, lazy way to make sense of modern American history is to measure it in decades. The revolutionary ’60s, the paranoid ’70s, the artificial ’80s, the alternative ’90s, the high-speed aughts.

What, then, of this decade in the United States? It’s not far gone enough to be understood or encapsulated. It’s essenceless. We don’t even have a name for it. The 10s? 21st Century: The Teen Years? Where and when did it really begin — nearly a year early, on the steps of the Capitol, with the jubilant inauguration of Obama? Or on Jan. 21, 2010, when the Supreme Court unleashed an ocean of money into the political process? Do we mark the decade by its parade of 21 movies in the “Marvel Cinematic Universe”?

Maybe the only person who can tell us when the decade started is Beyoncé, who owned it start to finish, from Sasha Fierce to “Homecoming,” through debt-ceiling crises and Taylor Swift and Hurricanes Sandy and Maria and Harvey.

“Who run the world?” Beyoncé asked 27 times in that anthem.

“Girls” was the answer each time.

At the start of this decade, women became the majority of the U.S. workforce (they still earned 74 cents for every dollar men made). This decade, for the first time, a woman was nominated for president by a major political party — and won a clear plurality of votes in the ensuing election (she lost anyway to a man accused of sexual assault by more than 20 people).

Way back in 2006, an activist from the Bronx named Tarana Burke started using “Me Too” on her MySpace page, as a refrain for survivors of sexual assault. We weren’t ready to listen to her. The phrase needed this decade for ignition. It needed hashtags and Twitter’s “trending topics,” which was introduced in 2010 to divine, distill and advertise widespread outrage and appreciation. It needed an accused predator in the White House, an online culture of virality and solidarity, and women who were fed up with being ignored by institutions, with keeping their hurt inside their heads. They exposed the system that all of us are living in, via the platforms that those systems had built.

“Indelible in the hippocampus is the laughter,” said a woman named Christine Blasey Ford, under oath, to the Senate Judiciary Committee in September 2018. Her trauma — decades old, buried, personal — now belonged to the public.

Being alive in the 2010s meant seeing what America wants to be, and feeling what it actually is. It meant feeling a bit of uplift while on a downward slide. Our self-diagnosis was “late-stage capitalism.” It explained our wanton ennui. It explained why Dr Pepper dangled $100,000 tuition checks during halftime competitions at college football games. It explained why families in Congo are suing five American tech companies for injuries endured by children mining for materials that end up in our phone batteries. It explained why Amazon stationed ambulances at one of its stifling warehouses as its employees worked themselves into unconsciousness.

Amazon “is running a continual performance improvement algorithm on its staff,” a former Kindle marketer told the New York Times. (Amazon CEO Jeff Bezos, the richest person on Earth, bought The Washington Post this decade.)

We stream. We swipe. We can watch anything, hear anything, order anything. Instantly. It’s not enough. For all the early talk of hope, Americans are becoming unhappier, according to a recent United Nations report.

The current U.S. birthrate is the lowest in 32 years. In 2015 life expectancy began to decline for the first time in 60 years. Over this decade, addicts turned from prescription opioids to heroin to fentanyl; since 1999 the risk of death from drug overdoses spiked 909 percent for people ages 55 to 64. The largest relative increase in contemporary suicide rates occurred among children ages 5 to 14, according to a report in the Journal of the American Medical Association. This decade started in the wake of a Great Recession — followed by mass demonstrations against Wall Street and the 1 percent — and will end with the 400 wealthiest Americans paying a lower tax rate than anyone else. This decade, for the first time in human history, the concentration of carbon dioxide in the atmosphere exceeded 415 parts per million — exactly as Exxon predicted 40 years ago, before it began to promote climate denialism that remains alive and well.

What is going on here, America?

Being alive in the 2010s meant waiting to be slain with a gun, or waiting to hear that someone you knew had been slain. In an accident, or a drive-by. In an encounter with a police officer in suburban Minnesota, or with a neighborhood watch volunteer in a gated community in Central Florida, or on the streets of Ferguson, Mo. During a mass shooting: in a church, in a dance club, in an office park, at a country-music festival, a congressional meet-and-greet, a congressional baseball game practice.

“All my friends are dead,” said a 6-year-old girl after a shooting massacre at her elementary school in Newtown, Conn., in 2012.

“All my friends are dead,” said a 98-year-old man after a shooting massacre at his Pittsburgh synagogue in 2018.

“Push me to the edge,” sang young rapper Lil Uzi Vert in his debut album. “All my friends are dead.”

It has become very easy to revel in bad news, and very easy to block it all out. In this decade we finally awoke to the direness of climate change, and this has inspired both sweeping activism and contagious nihilism. There are now infinite ways to numb anxiety, to thwart boredom, to ratify your own beliefs and prejudices in defiance of reality. A planetary threat becomes a hoax. A constitutional investigation becomes a witch hunt. A coalition becomes a conspiracy. Change becomes loss, or a sense of loss.

As of 2014, Latinos outnumbered whites in California.

As of 2019, a majority of domestic-terrorism cases investigated by the FBI were related to white supremacy.

Millennials became the most populous generation this decade, but owned a seventh of the wealth that the baby boomers had at their age.

“It feels natural,” Chelsea Manning, her prison sentence commuted by Obama, told Vogue about her gender transition. “It feels like it’s how it’s supposed to be, instead of this anxiety, this uncertainty.”

“Ungrateful TRAITOR,” Trump tweeted about Manning, six months before announcing a sudden ban on transgender people serving in the military.

Donald J. Trump. How can a decade be intact when it was bisected by his campaign and election?

Trump started the decade as a waning TV personality, a donor to the Clinton Foundation, a bankrupt casino owner looking for validation.

Trump ended the decade as the 45th president of the United States, all-powerful but resentful, impeached but uncowed, calling the free press “the enemy of the people,” claiming that the Constitution gives him “the right to do whatever I want,” joking that he might serve more than eight years, making more than 15,000 false statements during his term, mortgaging an entire political party to pay for ego and revenge.

Maybe the decade didn’t start until he did — on Aug. 6, 2015, on a mild summer evening in Cleveland, when Trump was asked his first-ever direct question as a presidential candidate in a debate.

“You’ve called women you don’t like ‘fat pigs,’ ‘dogs,’ ‘slobs,’ and ‘disgusting animals,’ ” said moderator Megyn Kelly, as a giggling horror rippled through the crowd. Trump interjected, with a finger in the air and an entertainer’s timing.

“Only Rosie O’Donnell.”

The lusty hollering that followed — it’s worth another listen. It’s the sound of something coming apart, or cracking open. The laughter: indelible. The ugly: exposed. The system: shook.

“No, it wasn’t,” Kelly rejoined, but the train had left the station.

“Thank you,” Trump said, speaking instead to his new followers, who were throwing their heads back, lifting their hands in a strident ovation, caught in a bad romance.

Four years later, with nine days left in the decade, Trump spoke to hundreds of young Americans in West Palm Beach, Fla. The artifice was long gone.

“The Democrat Party is trying to shred our Constitution, tear down our history, erase the nation’s borders,” he told the summit of conservative college students, dressed in suits and red hats, another snapshot of the era.

“Build the wall!” the young Americans chanted. “Build the wall! Build the wall!”

A decade is a construction; maybe Trump is building the one we’re living in. He chose a plot where the bedrock of cruelty and prejudice was deep and sturdy, but where demographics were reshaping the beachfront. He promised lux amenities — a higher and higher stock market, a larger and larger military, a big and beautiful wall — that had hidden costs. He said “I alone can fix it,” and then he took up his sledgehammer.

He declared his candidacy in 2015; he might leave office in 2025.

Maybe the decade is not over at all.

Maybe it is only halfway through.