On Thursday night, the U.S. military unleashed a 20,000-pound bomb — one of the largest nonnuclear weapons in its arsenal — on a tunnel complex the Pentagon said was used by Islamic State fighters in eastern Afghanistan.
It was a dramatic escalation of American operations against the militant group's affiliate in South Asia. It also came four days after a U.S. special forces soldier was killed alongside Afghan forces battling Islamic State fighters in the same district.
Afghan officials said several militants were killed, but there was no immediate information about civilian casualties as U.S. and Afghan forces continued operations in the mountainous area on Friday.
As a candidate, President Trump once vowed to "bomb the hell out of [Islamic State]." But the use of the Massive Ordnance Air Blast — known at the Pentagon as MOAB, or the "mother of all bombs" — came as a surprise because the group isn't seen as a major international threat.
Here's a primer on Islamic State's presence in Afghanistan and what the bombing could mean for a conflict that is in its 16th year:
What is Islamic State’s affiliate in South Asia?
Islamic State in Khorasan Province, as the affiliate calls itself, is made up largely of militant commanders from neighboring Pakistan and disaffected members of the Taliban, Afghanistan's main insurgent group. Khorasan is a historical name for a region that includes parts of present-day Afghanistan and Pakistan.
Far from its base in Iraq and Syria, Islamic State announced its presence in Afghanistan in early 2015 but has not been able to expand beyond a few districts in the eastern province of Nangarhar, along a rugged, porous stretch of the Pakistani border.
The militants have proved unpopular with Afghan villagers, who resent their attempts to ban poppy cultivation, and have been pummeled by both the Taliban and U.S.-led coalition airstrikes. A U.S. drone strike killed the group's former leader, Hafiz Saeed Khan, in Nangarhar last July.
Analysts say the group has sustained itself thanks to extortion, kidnapping and funds from Islamic State's central leadership.
How serious a threat does Islamic State in Khorasan pose to U.S. and Afghan interests?
From an estimated 1,000 to 3,000 fighters about a year ago, the Pentagon believes Islamic State's forces in Afghanistan have been whittled down to between 600 and 800 — concentrated in three border districts of Nangarhar.
The Taliban is far and away the bigger and more powerful insurgent group in Afghanistan. But U.S. officials worry the Islamic State presence is attracting foreign militants from Central Asian and Arab countries, complicating efforts to end hostilities and forge a peace agreement between the Taliban and the Afghan government.
And Islamic State has shown a willingness to inflict heavy civilian casualties. Last year the Sunni Muslim group claimed responsibility for bombing a demonstration by minority Shiites in Kabul, killing more than 80 people and wounding hundreds.
It has also claimed other deadly attacks in Afghanistan and Pakistan, including against a military hospital in Kabul last month, although some experts believe the group exaggerates its exploits.
Does the bombing represent an intensification of the U.S. war in Afghanistan?
It's hard to say. Trump has hardly spoken publicly about Afghanistan — he hasn't even appointed an ambassador — despite having 8,400 U.S. troops deployed there conducting training and counter-terrorism operations.
But it's clear that the pace of U.S. air operations has quickened since Trump took office. U.S. warplanes fired 403 weapons in Afghanistan in February and March, according to Air Force statistics, the most in a two-month period since 2014.
Pentagon officials have said they want to send more troops to help support Afghan forces — but the Afghans' biggest challenge remains the Taliban, which are inflicting heavy casualties among Afghan soldiers and civilians, and control territory where more than one-third of the population lives.
If analysts say the Taliban threat is greater, why was such a huge bomb aimed at a lesser militant group?
"One of the questions is: Why such a disproportionate level of response?" said Timor Sharan, an Afghanistan analyst with the International Crisis Group. "[Islamic State] might have killed one or two American soldiers, but the Taliban have killed thousands of American soldiers over the last 15 years."
How will this affect U.S. relations with Afghanistan?
Reaction to the bombing was mixed. The Afghan government, which worried that the Obama administration's slow withdrawal of U.S. troops would leave the country vulnerable to the Taliban, has lobbied Trump to increase U.S. involvement.
On Friday, Afghanistan's chief executive, Abdullah Abdullah, said in a series of tweets that the U.S. bombing was conducted "in coordination with the [Afghan] government," and showed "our common resolve to eliminate [Islamic State] and terror safe havens from our country."
But Omar Zakhilwal, Afghanistan's ambassador to Pakistan, called it "reprehensible" — and many Afghans worried that the "mother of all bombs" could serve as a recruiting tool for Islamic State.
Could Trump have intended the bomb as a warning to other adversaries?
Throughout its history, Afghanistan has seen its landlocked territory used as a pawn by bigger powers — from the 19th century "Great Game" between Britain and Russia to the Cold War, when the U.S. backed Afghan rebels against a Soviet occupation.
Many fear the bombing is the latest example of Afghanistan being exploited as part of a wider geopolitical agenda.
U.S. and Afghan officials have been worried by reports that Russia is strengthening ties with the Taliban, seeking to stop Islamic State from creeping into Central Asia. The bombing could be seen as an effort to show that coalition forces are on the offensive against Islamic State, countering Russian influence.
Trump has already shown a greater willingness than Obama to use American military power, launching missile strikes against Syria last week in retaliation for President Bashar Assad's suspected chemical attack against civilians. And fears are growing that Trump could strike North Korea if it tests a nuclear weapon.
Sharan said Thursday's bombing "sounds more like a message to the international rivals, including Russia and even North Korea, than actually a serious attempt by the Trump administration to get more deeply involved in the Afghan war."
Special correspondent Sultan Faizy contributed to this report from Pandola, Afghanistan.
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