There’s no safe place within Ukraine to manufacture shells or other war supplies. Russia can strike anywhere with their missles.
Least we forget Belarus. Ukraine always has to protect that border.
ISW: Russian Offensive Campaign Assessment, June 14 | Institute for the Study of War
Right, Russia is the most artillery-forward of any major power. Here’s a 2018 summation of the Asymmetric Warfare Group’s 2017 handbook on Russian tactics:
…Russian tactics still emphasize artillery as a decisive instrument for destroying enemy formations, while maneuver units handle mopping up the survivors…
Moscow has long been wielding more and bigger guns as a means to compensate for its forces’ qualitatively inferior training. Whereas Western militaries increasingly use artillery to launch precision strikes against enemy positions, the Russian army still values large-scale area bombardments with overwhelming volumes of firepower.
What do we even keep a military-industrial complex, if not to go all-in for a time like this!?
Because our military-industrial complex is useless to Ukraine unless they can transition to our weapons. It’s a less severe version of the warplane problem: they have to adapt their training to the new weapons, they have to adapt their logistics to the new ammunition, they have to field the new guns, they have to crank up their already limited import and distribution system to get all their Western largesse where it can do some good.
Artillery is easier to operate than warplanes, but every weapon system comes with its own fielding, logistics, training, and support demands.
It’s not all interchangeable.
I feel like it would be faster and easier for us to start making ammo for their systems.
Remember how long it took us to start making fabric masks?
Ukraine may have to adapt their training and use shells more tactically. Use forward artillery observers to make hits more effective. Instead of firing rounds as fast as possible day after day.
It does seem like US Cold War stockpiles could supply more than 18 howitzers. We should have dusty warehouses that haven’t been opened since the Gulf Wars. That’s what Russia is using.
https://www.cnn.com/2022/06/15/politics/biden-admin-ukraine-military-aid/index.html
I don’t see what makes that package add up to a billion dollars. Each M777 howitzer costs less than a million. The shells are each only a few thousand dollars. The Harpoon systems can’t be more than a few million bucks. What else is in there?
Shipping and handling?
I’m sure neither the Pentagon nor Ukraine want to publicize a comprehensive list of what the package includes. There’s no reason to spoil the surprise for the Russians.
General Mark Milley, Chairman of the Joint Chiefs of Staff:
I dunno about armor but when you have losses in infantry that large you start worrying about morale collapse.
Yes, but what percent has Ukraine lost?
The outlook for holding Donbass looks grim. And once Russia gains control there, what’s to stop them from offering a cease-fire, regrouping, and making another push for the rest of a weakened Ukraine in a year or two?
The Russians can offer a cease-fire all they want; Ukraine is under no obligation whatsoever to accept.
I don’t see any evidence that Russia is inexorably gaining territory – from what I’ve been following, they’ve had very sporadic, halting gains in territory, but also losses, and quite frequently losses shortly after they gain a piece of territory. Gaining territory is one thing; holding it is quite something else.
My gloomy assumption was that Ukraine would be sufficiently weakened as to have no choice but to accept.
So maybe my assumption is too gloomy. 
Their inevitable demographic collapse. In a year or two they will have less soldiers than they do today.
They may have more than they started with through captured Russian and Western-donated tanks.
News reports from a couple of months ago were that Ukraine has more tanks than the Russians:
Ukraine Now Has More Tanks on the Ground Than Russia: US Official Says.
The actual quote is that the Ukrainians have more tanks “in Ukraine”, not “on the ground”, which has an implication that they’re in use.
I would imagine that there might be an issue with trained tank crews. It’s one thing having tanks, another having the crews to use them. Ukraine will surely have lost some tank crews in battle, yet may be gaining in numbers of tanks. So I don’t know how big Ukraine’s reserve pool of trained tank crews is, or whether it would be large enough to put all these new tanks into action right away.
Don’t quote me on this, but I thought I read that tank crews in WWII had something like a year’s training before being deployed - many months of training, at least, as with the training for other types of soldiers.
Russia has the ability to manufacture low-tech hardware, pretty good. They also have a good supply of gas. That’s not a bad basis for building up a strong army.
But, be that as it may, Ukraine will have the whole world manufacturing for them, with no limit to access high end hardware. Particularly in the sky, Ukraine is going to go from way behind to complete domination over the next few years, I would expect.
Whatever Russia is able to get now is liable to be what they’re going to have until they lose it again. There isn’t going to be a second invasion - or at least not a successful one.