With the news that the U.S. will now send a small number of ATACMS to Ukraine, and of course over a year of asking why we haven’t sent them, I thought I’d do a little analysis of the numbers we could send.

Overall, it looks like the U.S. bought just under 3000 ATACMS over the years. The ATACMS actually went out of production years ago, then production re-started to meet Foreign Military Sales. But the U.S hasn’t bought new ones in a very long time and has no plans to do so. Instead, a new missile, the Precision Strike Missile (PrSM) will be available (“Early Operational Capability”) shortly (FY24). It won’t reach Initial Operational Capability and enter full production until FY25 or reach Full Operational Capability until FY27. Enough inventory to allow retirement of the ATACMS doesn’t happen until sometime in the 2030s.

That the U.S. purchased 3000 ATACMS doesn’t mean that is what the U.S. current has in inventory. Looking at various sources that show wartime usage, but having to guess at training and testing use, there are about 2300 ATACMS left in U.S. inventory. That could sound like a lot or a little to you, in reality it is a pretty small number. We have some data points that can show that. For example, the U.S. Air Force thinks in terms of there being 100,000 aim points (aka discrete targets) in a major regional war. The U.S. Army sees a lot more, and indeed we know that Ukraine has expended somewhere between 1 and 2 Million 155mm artillery shells alone so far. PrSM Increment 1 has an Inventory Objective of almost 4,000 (and then there are additional increments), so at a minimum the Army sees 4000 aim points for a missile in the same class as the ATACMS.

There are, sadly, a lot of targets in war. 2300 ATACMS seems like a drop in the bucket in that context, and that was before Russia’s invasion of Ukraine reinforced that western countries had allowed munitions inventories to drop far below what is adequate in wars between nation-states. With PrSM still a few years from full production, and other deep strike weapons (e.g., JASSM) running into production limits, the U.S. inventory of ATACMS is a critical resource that can’t be significantly reduced for a few years.

Those 2300 remaining ATACMS are not of a uniform type. Over half of the original 3000 were of the original M39 (ATACMS Block I) type. These have a cluster munition warhead, a maximum range of 165km, and INS-only (i.e., no GPS) guidance. The second largest type purchased was the M39A1 (ATACMS Block IA). That adds GPS and extends the range to 300km. After that the U.S. started buying versions with a Penetrating Blast-Fragmentation Warhead rather than cluster munitions. The initial version of that was the M48. An improved version is the M57. The U.S. has about 100 M48 and a little under 500 M57 remaining in inventory.

When you think about going after the Kerch Bridge and similar targets, think M48/M57. We just don’t have much to give away. But that isn’t the end of the story.

Since 2017 the U.S. has been remanufacturing the M39 and M39A1s into what is known as the M57E1. That’s an M57 with a new proximity fuze that allows an optional airburst for wide area effects, partially replacing the capability of the cluster munitions. So, the M57E1 is the most versatile ATACMS variant but we aren’t buying new ones (again, PrSM is coming). What isn’t clear is how many M39/M39A1s have already been converted to the M57E1. Hundreds certainly. We also don’t know the split between remanufactured M39s and M39A1s. On the surface remanufacturing M39s first makes more sense, because their shorter range, lack of GPS, and age (requiring a service life extension) makes them obsolete. And while the U.S. has been moving away from cluster munitions, it keeps some inventory in case of emergency. In that case, you’d want to retain some M39A1s.

Now the question comes up, what ATACMS might you supply to Ukraine? Some press articles have suggested they will be a cluster munition variant. We don’t know how many M39s are left in inventory, but frankly I don’t understand the utility of sending those to Ukraine. They don’t have the range or accuracy to meaningfully improve Ukraine’s capabilities. It’s not that the cluster munition warhead doesn’t add capabilities that nothing else provides, but volumes of M39s just wouldn’t be high enough under any conditions to make a substantial difference. Finally getting deliveries of the GLSDB going is going to be more impactful against targets in the 150km range, and hopefully that happens before the end of 2023. That leaves the M39A1s as a possibility.

There were 610 M39A1s produced. 74 were fired in Operation Iraqi Freedom. Others would have been fired in test and training. So, we can estimate there were around 500 in inventory before remanufacturing to the M57E1 started. The last contract (2021) for remanufacturing of M39/M39A1s to M57E1s that I can find ends in 2024. Projected funding for FY25 is half of what is allocated to the FY24 for completion of the 2021 contract, so it appears there are a few more missiles to remanufacture after the 2021 contract completes. I can’t tell if at that point there are no M39/M39A1s remaining, if any remaining M39s are headed for the scrap heap, and/or if we are still going to hold some M39A1s in reserve in case we desperately need a cluster munition. Any way you try to rationalize the numbers, the U.S. ends up with at best perhaps a couple of hundred M39A1s left after we end remanufacturing. One interesting possibility is that you end remanufacturing with the 2021 contract, leaving whatever was left with the projected FY25 funding (which perhaps you can redirect to PrSM) available to send to Ukraine. Good progress on PrSM makes that a low-risk approach to managing U.S. inventories. On the numbers front my best guess is that leaves at most 100 M39A1s that could be provided to Ukraine.

On the Penetrating Blast-Fragmentation (aka Unitary) warhead front there is a somewhat unique opportunity for delivering missiles to Ukraine. The 100 or so remaining M48s are known as the Quick Reaction Unitary (QRU) missiles. They were an interim buy while the M57 was developed. With most of the M39/M39A1s remanufactured into the M57E1, the U.S. could standardize fully on the M57/M57E1 and eliminate the remaining M48s from inventory. Those 100 M48s seem ripe for transfer to Ukraine.

When you get down to it, I’d estimate there are at most 200 ATACMS that the U.S. could spare, split between the M48 and remaining M39A1s. If we send any remaining M39s that would otherwise be scrapped, the numbers will sound larger, but the impact will be far less significant.

Now some caveats. I’m just an observer doing analysis of open-source information. There is information I might not have, and analysis where I am wrong. I don’t try to cover everything (e.g., the U.S. will soon deploy the Extended Range GMLRS that better addresses the targets that the M39 would have been used for). There are wildcards as always. I’ll even give one. A few weeks ago, it was reported that we “found” more ATACMS, and then that was denied. I suspect what “they” really meant is that the mix of ATACMS was a little different than the numbers they’d been working with. If “they” were looking at a post-remanufacturing Inventory Objective of say 2100 missiles and ignored that total inventory was actually 2300 (including remaining M39/M39A1s), it might seem that 200 more ATACMs had been “found”. They were never lost; they were just not part of the planning assumptions. If you add those back into the planning assumptions, you’ve found missiles you could spare for Ukraine while the U.S. still meets its inventory objective.

Update (10/17/23): Looks like the U.S. did send some of the remaining 165km range M39s to Ukraine as the remains of one have been found after a strike on Russia forces. As I mention above, a useful capability but not the “game changer” everyone is thinking ATACMS will bring.