On Friday, the Department of Defense announcedyet another aid package for Ukraine. The package is valued at $400 million and includes additional High Mobility Artillery Rocket Systems (HIMARS), 155mm and 105mm artillery rounds, armored vehicle launched bridges, ammunition, as well as other equipment.

The DoD release explains that the Biden administration is dispensing this latest round of aid using the Presidential Drawdown Authority, which, according to the DoD, is the thirty-third time the administration has pulled from DoD inventories since August of 2021.

As it stands now, the U.S. Army produces about 14,000 155mm shells per month. Extrapolate that to a year, and that’s just 168,000 shells—less than a fifth of the number of 155mm shells the U.S. has given Ukraine in the past year. If all Ukrainian aid ended tomorrow, it would take the U.S. just under six years to produce enough 155mm shells to bring U.S. stockpiles back to pre-war levels.

This explains why the U.S. is looking to boost the production rate of these shells to 20,000 shells per month sometime this spring; but even then, it would take just over 4 years to replenish 155mm shell stockpiles. This is why the U.S. wants to increase that production more than fourfold, from 20,000 to 90,000 shells per month, by 2025. Congress has already provided the factories that produce 155mm shells $420 million, but the United States is projected to spend nearly $2 billion on boosting the production of 155mm shells this year alone. Even at that new production rate, it would still take eleven months and change to bring 155mm shell stockpiles back to pre-war levels, assuming the U.S. stopped giving Ukraine 155mm shells entirely.

And it still remains to be seen if the investment into the production of 155mm shells will result in the massive production increase the U.S. military expects. Time magazine recently published an article that gave readers an inside look of the Scranton factory, owned by the U.S. Army and run by General Dynamics, tasked with making 155mm artillery shells. The factory produces just over 11,000 155mm shells per month. Its 300 employees are already worked hard—the factory runs 24 hours a day, five days a week, and has an additional weekend shift. The men work around heavy machinery and three furnaces that burn at 2,000 degrees Fahrenheit to refine, process, and form the steel.

Even though the 155mm shells are less technologically advanced than other military aid the U.S. has given to Ukraine, making the U.S. military’s production goals come to fruition is a daunting task. For the 155mm shells, at least there are open factory lines and plenty of infrastructure for the U.S. military industrial base to start from. The same can’t be said about the gun that fires these shells. The M-777 Howitzer production line is closed, and CSIS claims that stockpiles of the weapon were already limited back in September when the U.S. had given 126 M-777s to Ukraine. That number has since risen to 160. In total, CSIS estimates that the U.S. military has only about 1,000 M-777 systems.

The U.S. military has provided the Ukrainians with more than 8,500 Javelins, a portable, shoulder-fired anti-tank missile system, but current production levels, split between Raytheon and Lockheed Martin, are only 400 Javelins per month. It’s a marked increase of previous production levels, which CSIS estimated sat at around 1,000 Javelins per year. Nevertheless, the U.S. has voluntarily given about a third of its Javelin stockpile over to the Ukrainians.

The U.S. has handed Ukraine about a third of its Stinger stockpile as well, amounting to over 1,600 of the shoulder-fired anti-aircraft system. But the production line for Stinger missiles is in worse shape than that of the Javelin, kept open only thanks to small amounts of foreign sales, according to CSIS.

Raytheon Technologies chief executive Greg Hayes previously brought up concerns about dwindling Javelin stockpiles in December 2022. “In the first 10 months of the war, we’ve essentially used up 13 years of Stinger production, and five years worth of Javelin production,” Hayes reportedly said. “So the question is, how are we going to resupply, restock the inventories?”