Seems like I heard some time ago that we are practically there and have been for a bit. It was something I caught on the radio or TV, so I can't speak to its veracity.
Campaign planning is an interesting activity. There is a lot of give and take between the personnel section, intel section, operations section, logistics section, etc. How much operational capability will be needed to achieve the strategic objectives? That will drive the number of units. The number of units will drive the personnel. That will drive the daily throughput of rations, bed spaces, tents, etc. vehicle numbers drive fuel stockpiles, ammo consumption rates, etc. A tank division in a high intensity conflict will consume a trainload of artillery ammo daily.
When Monty told the planning cell, "three divisions for D-Day is not enough. We need five," that change drove a ton of changes to the planning up to that point.
Some items are durable (tents, for example, can be stored for years, so can demobed vehicles, which is why we store old Bradleys in Arizona, which costs almost nothing). Ammunition becomes unreliable when stored too long. Fuel is more perishable. So you can see how much to store of what for how long gets complicated.
Then the military has to go to industry to produce those supplies. At a reliably low rate of production, we can get stuff fairly cheap. Ramp that rate up, and it gets expansive.
Europeans (and to a lesser the US) based those things the assumption that we would not have to fight Russia any time soon.
In 2014, they assumption started to look dodgy. In 2022, it was shown to be probably false so there is a bunch of ramping up on both sides of the Atlantic, but it is expensive and takes time.
