When Iran chose to attack U.S. forces at two Iraqi bases on Tuesday, it relied on its missile arsenal, which is considered the largest in the region.

The Pentagon confirmed Tuesday evening that Iranian forces fired more than a dozen ballistic missiles at the bases, though officials were not able to confirm what types of missiles may have been used.

"I don't even know if the people on the ground know that yet," Pentagon spokesman John Supple told the Washington Examiner.

A spokesman for U.S. Central Command, which oversees U.S. operations in Iraq, told the Washington Examiner that 10 of the missiles hit Al Asad air base, a joint Iraqi-U.S. facility in western Iraq. Five missiles targeted a base in Erbil in the country's north, but only one successfully hit the base. Pentagon officials could not confirm if the four failed missiles reached their targets or were shot down by air defenses.

While Iran has a large and diverse missile arsenal, experts told the Washington Examiner the country likely used what are known as short-range ballistic missiles in the attack, weapons with a range of 620 miles or less.

"If I had to guess, Iran relied on the Fateh class or any of its variants here," Behnam Ben Taleblu, a senior fellow at the Foundation for Defense of Democracies who studies Iranian security, said. "As a reminder, the Fateh class are Iran's most accurate missile."

The Fateh, which has been in service since 2004, is also capable of being fired from mobile launch platforms and is powered by solid fuel, meaning it can be quickly deployed. It can carry a payload of more than 1,000 pounds and is capable of carrying a conventional or chemical warhead, according to the Center for Strategic and International Studies.

Matthew Kroenig, a former CIA and Department of Defense analyst who studies missile defense at the Atlantic Council, said Iran might have also used Shahab missiles, which have a range of about 800 miles. He added that they were likely to have carried conventional warheads.

"No indication that it's a chemical or biological attack, though sometimes it takes a while to tell. Humans have to be infected and then get sick. Depending on what the agent is, it could take a couple of days for something like that to show up," he said.

Iran invested heavily in its missile stockpile following the Islamic Revolution in 1979. Decades of international sanctions limited its air force to a handful of archaic jet fighters; instead, it has focused on acquiring a wide range of missiles, some of which are capable of hitting Eastern Europe.

"They picked bases that are really big, where you can hit the base without hitting anyone," Michael Pregent, a former intelligence officer who studies the Middle East at the Hudson Institute, told the Washington Examiner. "Talking to people inside government, they're saying that they think that this was a 'save face' gesture by Iran because they picked big bases and they're using missiles that were accurate enough not to hit something."

The Al Asad air base is located in Iraq's western Anbar province and is a large and well-fortified facility. It is primarily used by Iraqi and U.S. forces and was one of the largest bases used during the U.S. occupation following the invasion in 2003. In addition to its three 13,100-foot runways, several U.S. land forces from the Army and Marine Corps have been stationed at Al Asad.

Pregent said that both Al Asad and the Erbil bases would likely be prepared for an attack like the one they experienced Tuesday night.

"Especially since our special operations missions are conducted out of that Erbil joint base. It's probably going to be the one that's most heavily fortified since it is the closest to the [Iranian] border," he said.

Pregent said sources inside the U.S. government have told him that there were no U.S. casualties in the attack, which is why he said he believes the attack was more a "show of force" than an all-out attack.

"You hit the Sunni region, where Al Asad is in al Anbar province, and then you hit the Kurds to send a message," Pregent said.

Kroenig also noted that a salvo of slightly more than a dozen missiles is relatively small, considering Iran's large stockpile.

"So, my read is that this was their attempt at a 'Goldilocks' type strike to show that they were striking back without provoking a major war with the United States," he said.