Scranton, Pennsylvania (CNN) — Inside a sprawling factory just off the President Biden Expressway in downtown Scranton, Pennsylvania, the future arsenal of Ukraine’s war effort is being forged, one red hot artillery shell at a time.

Running full-tilt, as it was on a recent January morning, the Scranton Army Ammunition Plant churns out roughly 11,000 artillery shells a month. That may seem like a lot, but the Ukrainian military often fires that many shells over just a few days.

To meet that demand, the Scranton plant is undergoing a massive expansion, fueled by millions of dollars in new defense spending from the Pentagon. It’s investing in new high-tech machinery, hiring a few dozen additional workers and will eventually shift to a 24/7 schedule of constant production.

“It’s certainly ramped up over the last year. As we bring in more modern equipment, it’ll be able to ramp up even further,” said Todd Smith, senior director of General Dynamics Ordnance and Tactical Systems, which operates the plant for the Army.

“Intensity has gone up,” Smith added. “Let’s just put it that way.”

The US and its allies have already sent nearly $50 billion in aid and equipment to Ukraine’s military over the past year. To keep that up, and to rebuild its own stockpiles, the Pentagon is racing to re-arm, embarking on the biggest increase in ammunition production in decades, and putting portions of the US defense industry on a war-footing despite America technically not being at war.

The Pentagon has allocated roughly $3 billion alone to buy munitions overseas from allies and to ramp up production at home. Some of that money will go toward producing what has become a staple of the war – 155 millimeter artillery shells.

The Army is planning a 500% increase in artillery shell production, from 15,000 a month to 70,000, according to Army acquisition chief Doug Bush. Much of that increase will be fulfilled by the Scranton plant, which makes a large share of the country’s supply of artillery shells.

Across the US, munitions factories are increasing production as fast as possible. A Lockheed Martin plant in Camden, Arkansas, is cranking out a series of rockets and missiles, including those used by the Army’s Patriot missile system – all of which are in high demand in Ukraine. Bush told reporters in January that the Army was standing up a new plant in Garland, Texas to make artillery shells, while an existing plant is being expanded in Middletown, Iowa that loads, packs and assembles 155 millimeter shells.

Bush told CNN the Army intends to double the production of Javelin anti-tank missiles, make roughly 33% more Guided Multiple Launch Rocket Systems (GMLRS) surface-to-surface medium-range missiles a year, and produce each month a minimum of 60 Stinger anti-aircraft missiles – which were “almost not in production at all,” according to Bush.

Stinger and Javelin missiles are some of the most critical and relied-upon munitions by Ukraine to thwart Russian ground advances and aerial assaults, who previously told the US that it needs 500 of each every day.

“We realized we had to really put our foot all the way to the floor,” said Bush.

A race against time

As the war in Ukraine stretches into its second year, the US and its allies face an acute problem – Ukraine is burning through ammunition faster than the US and NATO can produce them.

The topic of dwindling munitions supplies was front and center during a crucial meeting in Brussels this week. Members of the Ukraine Defense Contact Group, an alliance of 54 countries supporting the defense of Ukraine, talked head on about the challenges of continuing to keep Ukraine’s military well-supplied.

NATO Secretary General Jens Stoltenberg said on Monday that the “current rate of Ukraine’s ammunition expenditure is many times higher than our current rate of production,” which is putting “our defense industries under strain.”

Much of that strain is being shouldered by American defense contractors. But even as the US embarks on an historic effort to re-arm, there are questions about whether it’ll be enough. As Ukraine prepares for a much-anticipated spring offensive in the coming weeks, the US is still years away from reaching its expected level of increased weapons production.

“The war hinges heavily on defense industrial production, and these are critical investments that the US and ultimately Ukraine will benefit from, but the question is, were they made too late to affect what could be the decisive phases of the conflict this year,” said Michael Kofman, director of Russia Studies at the Center for Naval Analyses, a national security research non-profit.

“For Ukraine, the challenges are more immediate and medium term, while much of the added US production capacity appears to be two years in the future,” said Kofman.

Indeed, according to Bush, it will take anywhere from 12 to 18 months for the US to reach its “max” production rate of 70,00 artillery shells a month.

Replenishing US stockpiles

In addition to ensuring Ukrainian troops have the equipment they need, the US also has to keep up with orders of more equipment from allies – which have only been increasing.

“Many allies in Europe right now are increasing their orders for US military equipment as a result of the war, so that’s adding to demand for our production,” said Bush. Ukraine’s need “changes month to month,” he added, making it less predictable than foreign military sales which are typically known well in advance.

On top of that, the US has a lot of work to do in rebuilding its own stockpiles, which the war in Ukraine has left dangerously low in the eyes of some experts.

A recent report authored by Seth Jones, the director of the Center for Strategic and International Studies’ International Security Program, warns that America’s assistance to Ukraine has “depleted US stocks of some types of weapon systems and munitions, such as Stinger surface-to-air missiles, 155mm howitzers and ammunition, and Javelin anti-tank missile systems.”

Jones also told CNN that CSIS war games showed in a Pacific conflict, the US runs out of “key long range munitions,” like long-range anti-ship missiles, in “less than a week of the war.”

“If our whole strategy right now, especially in the Pacific, is deterrence, we want to deter conflict – a key part of deterrence is that you have the weapon systems and you have enough of them pre-positioned in key locations so that any actor who is considering the aggressive use of force knows that we mean business and we have those systems in place to use and we’ve got enough of them to use in a protracted conflict,” Jones said. “That’s not where we’re at right now.”

The Pentagon is working to speed things up as best it can. Part of that effort involves changing the way it structures work order for the country’s large defense contractors. The military often works off year-to-year contracts, which makes it difficult for industry partners to plan ahead with production and their workforce in order to meet the needs the military lays out for them.

“No defense company in their right mind is going to start producing munitions if by the end of every fiscal year, the Marine Corps, the Navy, the Air Force takes what it had allotted in budget and moves it to a different pet platform or program,” said Jones of CSIS.

Bush said the Defense Department is looking at longer-term contracts, which he agreed would provide “a more efficient supplier base.” A seven-year contract, for example, allows industry to plan its workforce and production long-term instead of working year to year, he said. And building out that workforce will be critical as more plants and more shifts could ultimately mean more jobs

‘The arsenal of democracy’

In Brussels this week, top US defense officials struck an optimistic tone about being able to deliver Ukraine what it needs.

“With unity and urgency, we will again deliver the support that we have promised to Ukraine,” Defense Secretary Lloyd Austin said. “We will put capabilities into the hands of trained Ukrainian forces so that they can be integrated together on the battlefield.”

America’s top general, Chairman of the Joint Chiefs of Staff Gen. Mark Milley echoed the same sentiment in a press conference on Tuesday, saying the international community “will continue to support Ukraine” until Russian President Vladimir Putin “ends his war of choice.”

But back home, there are questions about how sustainable the US commitment to Ukraine truly is. A poll published in December found that support for US aid to Ukraine was declining among Republicans, and there were concerns that a Republican-led Congress could lead to a drop in material support for Ukraine at a time when the rate of weapons production could make all the difference on the battlefield.

Last week, Republican Rep. Matt Gaetz introduced a bill to end US support for Ukraine, a measure supported by a handful of far-right lawmakers including Lauren Boebert, Marjorie Taylor Greene and Paul Gosar. GOP sources, however, have told CNN that it’s only a small group of Republican lawmakers who are against funding aid to Ukraine.

And though then-House Minority Leader Kevin McCarthy suggested in October that Republicans could slow funding for Ukraine if they took majority control, sources said he has since walked back his comments privately to reassure senior defense hawks in the House.

If all goes according to plan, in a year production rates in the US will be much higher than they are now, Bush said. And while the hope is that the conflict in Ukraine is over long before then, Bush is confident the US military and industrial base would be ready for whatever comes next.

“We are still the arsenal of democracy,” Bush said. “And nobody does it better than the United States.”