The Pentagon said Thursday that it had dropped the largest non-nuclear bomb ever used in combat, prompting questions about what exactly this weapon is.

Most of what is publicly available about the GBU-43 comes from a 2008 article from the Eglin Air Force Base. The piece, which marked the five-year anniversary of the bomb, says that the GBU-43 weighs a massive 21,600 pounds. During testing, the weapon created a mushroom cloud that could be seen 20 miles away from the blast, according to the Air Force story.

@CleverTalks: "Mother of All Bombs." GBU-43/B Massive Ordnance Air Blast Bomb. Dropped in Afghanistan 4.13.17. test footage.

@amanda_m_macias: USAF photos show a version of the MOAB used

Each MOAB costs around $16 million, according to military information website Deagel. With 20 made so far, the site says the U.S. military has spent some $314 million on the production of the explosive.

The original goal of the so-called MOAB — either standing for "Massive Ordinance Air Blast" or "Mother Of All Bombs," depending on who you ask — was to act as a non-nuclear deterrent against former Iraq dictator Saddam Hussein.

"The goal is to have the pressure be so great that Saddam Hussein cooperates," Defense Secretary Donald Rumsfeld said in a 2003 interview, according to the Eglin Air Force Base story. "Short of that — an unwillingness to cooperate — the goal is to have the capabilities of the coalition so clear and so obvious that there is an enormous disincentive for the Iraqi military to fight against the coalition."

The bomb was rapidly developed by the Air Force starting in 2002 as a replacement for the BLU-82 Daisy Cutter. While the MOAB was bigger, it was also smarter, with GPS-capable targeting allowing for more accurate bombing operations, according to the story.

But while the weapon was initially deployed to the Middle East back in 2003, this is the first time it has been used. Originally designed as a deterrent, it's now being deployed as an active tool in the war on terror.

"What's worse than unleashing on society the wrath of the largest non-nuclear bomb yet to be made?" the 2008 Eglin Air Force Base piece asked. "Letting the world know it's out there and ready to be used at any moment."

Correction: This story was updated to reflect that the MOAB is the biggest non-nuclear bomb dropped by the U.S. in combat.

Watch: We dropped a very large bomb, says Colonel