In this U.S. Air Force handout,  a GBU-43/B bomb, or Massive Ordnance Air Blast (MOAB) bomb, explodes November 21, 2003 at Eglin Air Force Base, Florida. MOAB is a 21,700-pound that was droped from a plane at 20, 000 feet.
U.S. Air Force/Getty Images
In this U.S. Air Force handout, a GBU-43/B bomb, or Massive Ordnance Air Blast (MOAB) bomb, explodes November 21, 2003 at Eglin Air Force Base, Florida. MOAB is a 21,700-pound that was droped from a plane at 20, 000 feet.
Now playing
00:57
MOAB bomb originally developed for Iraq war
Now playing
05:18
Anderson Cooper explains how he overcomes being shy
LONDON, ENGLAND - DECEMBER 07:  A visual representation of the digital Cryptocurrency, Bitcoin on December 07, 2017 in London, England. Cryptocurrencies including Bitcoin, Ethereum, and Lightcoin have seen unprecedented growth in 2017, despite remaining extremely volatile. While digital currencies across the board have divided opinion between financial institutions, and now have a market cap of around 175 Billion USD, the crypto sector coninues to grow, as it continues to see wider mainstreem adoption. The price of one Bitcoin passed 15,000 USD across many exchanges today taking it higher than previous all time highs.  (Photo by Dan Kitwood/Getty Images)
Dan Kitwood/Getty Images
LONDON, ENGLAND - DECEMBER 07: A visual representation of the digital Cryptocurrency, Bitcoin on December 07, 2017 in London, England. Cryptocurrencies including Bitcoin, Ethereum, and Lightcoin have seen unprecedented growth in 2017, despite remaining extremely volatile. While digital currencies across the board have divided opinion between financial institutions, and now have a market cap of around 175 Billion USD, the crypto sector coninues to grow, as it continues to see wider mainstreem adoption. The price of one Bitcoin passed 15,000 USD across many exchanges today taking it higher than previous all time highs. (Photo by Dan Kitwood/Getty Images)
Now playing
03:07
Bitcoin has an energy problem
Now playing
01:32
Scientists turned spiderwebs into music and it sounds like a nightmare
Jeopardy Productions, Inc.
Now playing
01:02
Aaron Rodgers' Green Bay Packers question stumps 'Jeopardy!' contestants
Now playing
05:18
Coinbase CFO: We're an on-ramp to the crypto economy
Kristina Barboza
Now playing
03:09
Grieving mom's advice to other families: You can try to help, support and love
CNN
Now playing
02:12
'Too dangerous to do anymore': Sacha Baron Cohen on Borat
Christopher Hamilton
Now playing
01:01
Volcanologist shares what he prefers to cook on lava flows
John Avlon 0413 Wallace
CNN
John Avlon 0413 Wallace
Now playing
03:31
Avlon compares Tucker Carlson's comments to George Wallace
screengrab hong kong oscars
IMDB / Field of Vision
screengrab hong kong oscars
Now playing
02:50
Hong Kong won't air Oscars for the first time since 1968
Now playing
01:27
See the first community of 3D-printed homes
Burlington, MA Headquarters
Nuance
Burlington, MA Headquarters
Now playing
01:34
Microsoft to buy AI company Nuance
Now playing
02:50
Sleep doctor tells Anderson Cooper how long a power nap should be
WASHINGTON, DC - DECEMBER 01: Chairman of the Federal Reserve Jerome Powell testifies during a Senate Banking Committee hearing about the quarterly CARES Act report on Capitol Hill December 1, 2020 in Washington, DC.  Treasury Secretary Steven Mnuchin also testified at the hearing. (Photo by Susan Walsh-Pool/Getty Images)
Susan Walsh/Pool/Getty Images
WASHINGTON, DC - DECEMBER 01: Chairman of the Federal Reserve Jerome Powell testifies during a Senate Banking Committee hearing about the quarterly CARES Act report on Capitol Hill December 1, 2020 in Washington, DC. Treasury Secretary Steven Mnuchin also testified at the hearing. (Photo by Susan Walsh-Pool/Getty Images)
Now playing
02:06
Fed chief: The economy is about to grow more quickly
"Saturday Night Live" / NBC
Now playing
01:47
'SNL' sees Minnesota news anchors take on the Derek Chauvin trial

Story highlights

The area targeted by the MOAB has always been difficult to attack

Craggy mountains and caves hewn from sheer rock have been hideouts for decades

(CNN) —  

Back in late 2001 when Osama bin Laden was US enemy No. 1, I spent a good bit of time in the Afghan mountains not far from where the MOAB was dropped.

Bin Laden’s hideout was Tora Bora, on the same mountain ridge in the Achin district of Nangarhar. We watched as American bombers flew lazy eights in the sky awaiting their bombing runs.

When the go was given, we could at times see stacks of bombs cascading toward the rugged and unforgiving mountainside.

What surprised me back then was the limit of the damage the bombs caused. Scrambling around the freshly cleaved boulders following the bombings, bin Laden’s tunnel entrances were still discernible; we could even clamber into a few.

At the back of some were mountains of ammunition: small and medium caliber rounds for AK-47s and heavier machine guns, perfectly preserved in their original tin and wood cases.

This area was simply hard to bomb effectively with the weapons available at the time. The mountains are craggy and rocky and the tunnels favored by bin Laden were tucked away in tight gullies so they were anything but an easy target. And with shelters hewn out of the solid rock, they were very robust, too.

In recent weeks the battle against ISIS in this area has been heating up, with scores of their fighters reported killed in US and Afghan ground and air strikes in the last 10 days alone.

Since ISIS first began putting down roots in Afghanistan, Nangarhar province has been a priority. And with good reason: it has relatively easy access to the tribal areas of Pakistan, which operate according to their own rules.

The mountains where ISIS made their base were the same ones used by bin Laden as a bolt hole and the same used by the CIA-backed mujahideen when they were fighting the Soviets in the 1980s.

It was from camps in these same hills that the mujahideen fought their way into the provincial capital city of Jalalabad, forcing the Soviets out of the airbase that is now a key strategic US military hub.

Long before bin Laden hid out in the mountains here, I spent time with local farmers. The Taliban were forcing them to stop growing opium poppies, but it was tough going.

Poppies bloom in a field on the outskirts of Jalalabad, capital of Nangarhar province in 2014.
Noorullah Shirzada/AFP/Getty Images
Poppies bloom in a field on the outskirts of Jalalabad, capital of Nangarhar province in 2014.

In the local villages, opium paste was still being traded by the kilo and there was plenty of money to be made. The tracks leading from the villages up into the mountains behind then went directly to Pakistan.

It was then, and is today, a porous border for all manner of smuggling. Commercial traffic takes the tarmac highway in the valley below to the fabled Khyber Pass, but if you are a drug smuggler or terrorist, a day’s detour into the hills will keep you safe from prying eyes.

It’s what makes crushing ISIS in this particular province so important. Many of their recruits come from just over the border in Pakistan. ISIS pays more than the Taliban, more than the Afghan army to young men ready to put their lives on the line.

If the MOAB landed on target, there is a good chance plenty of tunnels and ISIS equipment will have been destroyed, enough to disrupt their operations for a while.

Getting rid of them for good in terrain that historically favors hiding and evasion is going to be a tough, bloody and labor-intensive challenge, much as the US Afghan commander Gen. John Nicholson has been telling the White House. Today’s attack is but a step on the way.