officials testified before the US House Armed Services Committee, describing the major issues with the US fight against ISIS.

Former CIA Director Michael Morell, former US Undersecretary of Defense for Intelligence Michael Vickers, and former US Ambassador to Syria Robert Ford had common threads that outlined two major problems with the US strategy to defeat the terrorist group ISIS — aka the Islamic State, ISIL, or Daesh.

The first problem is that air power alone won't be enough to defeat the group.

The second, related issue is that there aren't local ground forces in Iraq and Syria that are capable of clearing and holding territory.

And while the US has been fighting terrorism directly in the Middle East for more than a decade, ISIS is a much more evolved version of America's old foe, al-Qaeda.

"I believe ISIS poses a significant strategic and lethal threat to the United States of America," Morell said.

He continued: "The nature and significance of the threat posed by ISIS flows from the fact that ISIS is at the same time a terrorist group, a quasi-state, and a revolutionary political movement. We have not faced the likes of it before."

The US has been fighting an ideological and a literal war with ISIS. At home, the US government has been working to counter ISIS's very effective online propaganda messaging, and abroad the military has been running airstrikes and training ground forces in Iraq and Syria.

The propaganda war isn't going well for the US, and the officials who testified on Tuesday emphasized that the air war is falling short as well.

"Air power is not gonna win this thing alone," Morell said. "We need a ground force."

Morell is more optimistic about Iraq than he is about Syria. This sentiment was echoed by Ford, who said that he was "much less upbeat, much less optimistic" about the Syrian side of the fight.

"There is a strategy in Iraq to get that ground force. Ramadi showed that that strategy has potential," Morell said. Ground forces backed by US air power recently drove ISIS out of the Iraqi city of Ramadi.

Still, Iraqi ground forces have a long way to go, Ford said.

"I worry, frankly, that we do not yet have enough people, friendly indigenous fighters, in places like Ramadi, Anbar Province, Diyala Province" to hold territory retaken from ISIS, he said. "I'm not sure that 30,000 [soldiers] is going to be enough to secure that Syrian border and control those towns."

Meanwhile, the US is struggling to figure out how to seize territory back in the first place in Syria.

"There is no ground force on the Syrian side that carries the same kind of potential as the Iraqi military carries," Morell said.

He continued:

We can do more, I think, with the moderate opposition, but at the end of the day, I think, [Syrian President Bashar] Assad's got to go, and we have to take the Syrian military [and] security resources, as degraded as they've become, and turn them into a force that the international community supports in taking on ISIS.

Ford agreed that Assad, whose forces have been known to barrel-bomb civilians and commit other atrocities, must be forced out if we want to see a successful ground fight in Syria.

"The only way to generate more indigenous forces is to help the Syrian opposition and to see the removal of Bashar al-Assad at some point and the creation of a new national unity government," Ford said. "The sooner that can be done in Syria, the better. Only a new national unity government in Syria is going to be able to mobilize enough Syrians to fight and destroy the Islamic State."

It's unclear, however, if Assad will be removed from power anytime soon. Russia recently jumped into the fray in Syria under the guise of fighting ISIS.

But it seems that Russia's real aim is propping up its ally the Assad regime, since much of Russia's airstrikes in Syria have hit anti-Assad rebels rather than ISIS fighters.

And while Russia has been increasing its presence in Syria, the US-led coalition has been focusing on Iraq.

"Two-thirds of coalition efforts have really been against Iraq and not against Syria, where the more dangerous threat has existed," Vickers said.

Syria is a much more chaotic theater than Iraq considering the all-out civil war that exists there, and ISIS's de facto capital and center of operations is based in Raqqa, Syria. The group is deeply entrenched there and US-backed forces haven't yet been able to take back Mosul, ISIS's main Iraqi base, let alone go into Raqqa.

And while the US has seen some success in training Iraqi forces, that has not been the case in Syria. In October, the US ditched its program to train rebels in Syria to fight ISIS. This came after reports that rebels had been told that they couldn't fight Assad or the regime's allies, including Iranian-backed militias in Syria.

Even if the US took the advice of experts who say Assad must go in order to achieve peace in Syria, it's unclear who would replace him.

"It has to be negotiation," Ford said.

"Had we asked the question 'Who would follow Saddam Hussein?' we wouldn't have known the answer to that in 2003," he continued, referencing the US toppling former Iraqi President Saddam Hussein after the 2003 invasion.

He said:

Just as the wobbly government in Iraq ... needed help, that will be the case also in Syria. I do not believe that if Assad goes, only the Islamic State takes over. I think that is wrong on multiple levels and is indicative of the sense that there is no hope, when actually there is quite a bit of hope.