The war in Afghanistan: A visual timeline of the 18-year conflict

Immediately after the 9/11 terrorist attacks, the rationale for invading Afghanistan was clear — wipe out al-Qaeda and overthrow the Taliban government.

Even though none of the hijackers or planners were Afghans, the Bush administration categorized Taliban leaders as terrorists because they had given al-Qaeda sanctuary and refused to hand over its ringleader: Osama bin Laden.

Within six months, the United States had achieved its goals. The leaders of al-Qaeda and the Taliban were dead, captured or in hiding.

Instead of withdrawing, however, the U.S. government started to blur its strategic objective — something that would persist for the next 17 years, according to a cache of confidential government documents obtained by The Washington Post.

Here is a look at nearly two decades of conflict through the lens of the documents and memos — and the shifting strategies along the way.

In 2001, after initial airstrikes by the United States and Britain on military targets, the United States sends about 1,300 troops to Afghanistan.

One after another, cities controlled by the Taliban begin to fall with the help of Afghanistan’s Northern Alliance soldiers.

By December 2001, the U.S. force grows to 2,500 as troops scour the mountainous Tora Bora region looking for bin Laden. The Taliban is largely ousted, and an interim Afghan government is established.

On Jan. 4, 2002, Army Sgt. 1st Class Nathan Chapman, a Green Beret working for the CIA, becomes the first military combat casualty.

Six days after Chapman’s death, Defense Secretary Donald H. Rumsfeld writes a memo:

“I think I want to write letters of condolence to the spouses, or parents if they have no spouse, of all who die in this Afghan war, whether it is in combat or by some other cause. Please see that we work up something like that.”

The defense secretary wrote thousands of confidential memos — dubbed “snowflakes” — during his time at the Pentagon. Many of the snowflakes foreshadow problems that continue to haunt the U.S. military.

“I may be impatient. In fact I know I’m a bit impatient,” Rumsfeld writes in one memo dated six months after the war started. “We are never going to get the U.S. military out of Afghanistan unless we take care to see that there is something going on that will provide the stability that will be necessary for us to leave.”

“Help!” he adds.

After victories in the early 2000s, President George W. Bush decides to keep a light force to ensure al-Qaeda will never return. To accomplish that, U.S. officials say it is necessary to help the Afghans build a stable government and launch reconstruction initiatives.

But the strategy runs counter to Bush’s early promise not to engage in nation-building.

In March 2003, U.S. forces invade Iraq, and Afghanistan becomes an afterthought. In a government document obtained by The Post, James Dobbins, a career diplomat, says it was a hubristic mistake from the start: “First, you know, sort of just invade only one country at a time. I mean that seriously."

Two months later, Bush declares an end to “major combat operations” in Iraq. On the same day, Rumsfeld visits Kabul and announces an end to “major combat activity” in Afghanistan.

But the conflict is far from over.

After serving as interim leader, Hamid Karzai is elected president in Afghanistan’s first national democratic election in 2004. He builds a personal rapport with Bush; the two leaders chat frequently by videoconference.

But relations gradually sour.

As the nation-building campaign continues, the U.S. military begins to train the Afghan national police force. But there are major challenges.

In a 2005 memo, Rumsfeld says the program is a mess and that he is “ready to toss in the towel."

By 2006, the Taliban is giving U.S. and allied troops all they can handle in the eastern and southern parts of the country. In a memo shared with Rumsfeld, retired Army Gen. Barry McCaffrey reports that the Taliban is resurgent and predicts it will take five more years “of continued robust U.S. military presence” to train Afghan security forces.

By the end of 2007, the number of U.S. troops rises to 25,000.

Still, Iraq is the priority. And security in Afghanistan worsens. The Taliban rebuilds itself, and parts of the country grow increasingly unstable.

In December 2009, President Barack Obama announces a troop surge: He will deploy 30,000 more U.S. troops to Afghanistan, on top of the 70,000 that he and Bush had previously authorized. NATO and other U.S. allies will increase their forces to 50,000.

Karzai wins reelection in 2009, narrowly avoiding a runoff thanks to a massive ballot-stuffing campaign. His opponents, and many independent observers, accuse his side of trying to steal the election. The outcome puts Obama administration officials in a box. They had promised to root out corruption, but they do not want to alienate Karzai.

In the end, U.S. officials swallow their objections.

“It was devastating that we were willing to patch up the elections,” Sarah Chayes, who served as a civilian adviser to the U.S. military, will later tell government interviewers. “While we had the opportunity to say that corruption is important, explicit instructions were given that it is not.”

In February 2010, coalition forces launch one of the largest military operations of the war, to retake Marja, in Helmand province, from the Taliban. Initially labeled as a military success, the operation fails to establish a long-term working government in the southern region. Large parts of the province eventually fall back into the hands of the Taliban.

The number of U.S. troops in Afghanistan reaches 100,000.

U.S. troops suffered more casualties in 2010 than in any other year of the war.

In May 2011, U.S. Special Operations forces kill bin Laden during a raid at a compound in Pakistan.

In June 2011, Obama orders a partial, staged withdrawal of U.S. troops from Afghanistan.

In December 2011, U.S. troops withdraw from Iraq.

Throughout 2012 and 2013, U.S. and NATO officials work to put Afghan forces in the lead for security across Afghanistan, despite worrying signs suggesting that local troops remain unequipped to keep the Taliban at bay without substantial foreign assistance.

In October 2014, the United States and Britain hand over two major bases — Camp Leatherneck and Camp Bastion — to the Afghan military, and on Dec. 28, 2014, the NATO combat mission, Operation Enduring Freedom, officially ends. It is replaced by two missions: Resolute Support, in which NATO forces provide training and support to Afghan forces, and Freedom’s Sentinel, in which U.S. forces continue to carry out Special Operations raids and other counterterrorism operations with some assistance from Afghan units.

But by the time Obama leaves office in January 2017, his promise to withdraw all U.S. troops has fallen short: 8,400 U.S. troops remain in Afghanistan.

His successor, President Trump, decides it is not enough. In September 2017, he announces he will sends back several thousand more U.S. troops to help the Afghans.

In 2018, Afghanistan ranks as one of the most corrupt countries in the world, according to the Corruption Perceptions Index released by Transparency International.

More than 775,000 U.S. troops deployed over the 18-year conflict, many repeatedly. Of those, 2,300 died in Afghanistan and 20,589 were wounded in action, according to Defense Department figures. More than 60,000 members of Afghan security forces have been killed, a casualty rate that U.S. commanders have called unsustainable. And estimates put the number of Afghan civilians killed in the war at more than 43,000.

Today, about 13,000 U.S. troops remain.

The Trump administration continues to escalate the war from the skies to prevent the Taliban from taking over.

A recent U.N. report declared 2018 as the deadliest year for civilians in the conflict. It noted a particular increase in child casualties from U.S. and coalition airstrikes.