Rebuilding U.S. Inventories: Six Critical Systems

As the United States transfers massive amounts of weapons, munitions, and supplies to Ukraine, questions arise about the health of U.S. inventories. Are inventories getting too low? How long will it take to rebuild those inventories? An earlier CSIS commentary identified those inventories that are at risk as a result of transfers to Ukraine. This commentary continues that analysis by examining inventory replacement times. Most inventories, though not all, will take many years to replace. For most items, there are workarounds, but there may be a crisis brewing over artillery ammunition.


The table below lays out weapons and munitions where concerns have arisen about inventories.

Note: The table is built from DOD sources plus estimates based on administration statements, news reports, interviews with officials, and the author's experience in the military as an artillery officer and with acquisition in the Pentagon. The number transferred to Ukraine comes from periodic DOD fact sheets. Production rates come from DOD budget documents, particularly the Army's procurement justification books for missiles and ammunition. "Recent" production reflects levels funded in the last few years. "Surge" reflects higher rates where DOD has said it would increase production. This higher rate is either the "1-8-5" or "MAX" level depending on where current production is. It takes one to two years to get to this higher level. For munitions, the production applied to rebuilding inventories is reduced to account for U.S. peacetime training and stockpile testing. “Manufacturing lead time” is the period between when a contract is signed and when the first item arrives. This interval is typically about 24 months but varies by system. “Production time” is how long it would take to produce all the required inventory. “Total time to rebuild” includes both manufacturing lead time and production time. The color code indicates the difficulty of the rebuilding effort.

System Details

155 mm ammunition. This category consists of a wide variety of non-precision projectiles, mostly the basic high explosive (HE) shell (M795) but also specialty shells like extended range HE, smoke, illumination, and marking (white phosphorus). The United States has provided about 1,000,000 projectiles to Ukraine. It continues to provide some, though these may be pass-throughs from allies like South Korea who don't want to transfer lethal aid directly. Military planners appear to regard this as the most serious shortage since artillery constitutes the backbone of ground-based firepower.

Rebuilding inventories at the current production rate is probably not possible because of routine U.S. training needs. Artillery units must fire a certain number of rounds every year to be proficient. Simulators can provide only a small substitute because of their limited ability to replicate all elements of the firing process. Annual training requirements are likely equal to the recent production levels since these programs have been around for a long time, the budget levels have been relatively constant for several years, and there has been no need to increase inventories.

Current production is 3,250 per month. DOD says that it can get that rate up to 20,000 per month (240,000 per year) by the spring of 2023 and 40,000 per month (480,000 per year) by 2025. At this surge rate, it would take about six years to rebuild inventories allowing for normal peacetime usage and assuming no further transfers from inventory.

That is a big assumption because of Ukraine’s high shell usage. In April, the United States announced it was sending 155 mm howitzers to Ukraine. Those probably arrived in May and began firing intensively in June. It is not clear how many of the million rounds they have used in the six months of operations, but, assuming Ukraine has one month of artillery ammunition left on hand, that comes out to 143,000 rounds fired a month, or about 4,800 rounds per day. Combined with shells fired from Ukraine's Soviet-era artillery, this is in the vicinity of the 6,000–7,000 per day that Ukraine has said it was firing (and which was considered inadequate). Even the 2025 surge rate would satisfy only a third of this need. To bridge the gap, other countries will have to provide ammunition, and a lot of it.

This could become a crisis. With the front line now mostly stationary, artillery has become the most important combat arm. Ukraine will never run out of 155 mm ammunition―there will always be some flowing in―but artillery units might have to ration shells and fire at only the highest priority targets. This would have an adverse battlefield effect. The more constrained the ammunition supply, the more severe the effect.

As an offset, the United States has provided 105 mm howitzers and ammunition―36 howitzers and 180,000 shells. Because these shells are lighter and have a shorter range, the number of howitzers and shells will need to be very large to provide an adequate substitute.

155 mm precision (Excalibur). In 2007 the United States fielded Excalibur, an artillery shell guided by GPS. The firing unit has only to input the coordinates, and the projectile guides itself to the target with an accuracy of two meters. This projectile is far superior to the previous precision artillery munition, Copperhead, which required a spotter using a laser designator. A complementary system, called Cannon-Delivered Area Effects Munition (C-DAEM in the budget documents), is also GPS guided but uses submunitions to attack personnel and vehicles. It is just being fielded. (The Army needs a better name here, as a CSIS colleague has argued.)

DOD says it has sent 5,200 "precision-guided 155 mm artillery rounds" to Ukraine. Assuming these are all Excalibur, then it will take 84 months (7 years) to replace the inventory at the recent production rate and 48 months (4 years) at the surge rate.

The long-range precision guidance kit, a cheaper but slightly less accurate precision guidance system also exists. It consists of a mechanism screwed into the nose of a standard artillery projectile, thus greatly expanding the potential inventory of precision munitions. However, the program is just finishing development and has not yet entered full-rate production, though it might be available in the future.

Ongoing battlefield usage constitutes the great challenge here. The United States has been sending about 1,000 of these precision projectiles per month. However, Excalibur's annual production is only about 1,000. Total production since the beginning of the program has been about 15,000, but many of those were expended during the wars in Iraq and Afghanistan and for testing and training. The inventory is thus likely to be small, and the United States may soon run out of Excalibur projectiles to send.

GMLRS (described below) may provide an alternative, but the number of HIMARS launchers (20) is much more limited than the number of howitzers capable of firing Excalibur (146).

Javelin. Javelin, a long-range, infantry portable precision anti-tank missile, became the iconic weapon of the early phases of the conflict. It was easy to use, provided in large numbers, and, as a result, instrumental in stopping the initial Russian offensive. The United States has provided 8,500 to Ukraine. However, further transfers have stopped because inventories are at the point where the risk to other war plans, for example, a conflict on the Korean Peninsula or in the Baltic countries, has become too high.

At the recent production rate of about 1,000 per year, it will take 149 months (12.5 years) to rebuild the inventory to the pre-conflict level. At the accelerated rates that DOD and Lockheed Martin have announced, it will take about 80 months (6.5 years). This assumes no further transfers and no diversion of production to other allies.

The government has begun this process. Congress authorized multiyear procurement of up to 12,050 Excalibur rounds, and DOD recently awarded an $84 million contract for 1,000 rounds.

High Mobility Artillery Rockets System (HIMARS). If Javelin was the iconic weapon of the early phases of the war, HIMARS is the iconic weapon of the later phases. Although "HIMARS" is often used to refer to both the launcher and the missile, this analysis refers to the launcher, a modified heavy truck with rocket pods on the back. (The United States has a tracked version of the system for armored units, called the Multiple Launcher Rocket System (MLRS) but has not yet transferred any to Ukraine. However, the United Kingdom and Germany have together sent 10.)

The United States has transferred only 20 HIMARS to Ukraine. Because numbers are so low and the production line is hot, replacement of the transferred articles will not take long: at the recent production rate, three years, and at the surge rate, two and a half years. Indeed, DOD recently let a $431 million contract to Lockheed Martin for increased HIMARS production.

Ukraine’s challenge is that it has only 30 systems (including MLRS) to cover 530 miles (850 kilometers) of active front. That means just one system per 18 miles of front. Ukraine needs more. However, the United States has been reluctant to take systems from existing U.S. units or to provide the heavier and more complicated MLRS system. (Note: The DOD fact sheet cites 38 HIMARS provided, but 18 will be new production and not delivered for several years.)

Guided Multiple Launch Rocket System (GMLRS). This is the guided munition that HIMARS fires. Because of its long range (about 45 miles) and high accuracy (within 10 meters), it has apparently been devastating to Russian logistics hubs and headquarters units. DOD has been tightlipped about how many it has sent to Ukraine, saying only "thousands." Similarly, the usage rate is unclear, with General Milley, chairman of the Joint Chiefs of Staff, saying in early September that Ukrainians had hit 400 targets using HIMARS. Since the systems had been in Ukraine about a month, that would indicate a relatively low rate of usage. A low usage rate is also consistent with the small number of launchers.

The recent U.S. production rate is 5,000 rockets per year and could increase to 10,000 per year or more. That would be adequate to handle 400 rockets a month. Further, the United States has a relatively large inventory. DOD has received about 50,000 rockets since the beginning of the program, though many were used for training and testing and in combat in Iraq and Afghanistan. The remaining inventory is probably 25,000 to 30,000. If DOD gave a third to Ukraine, that would provide 8,000 to 10,000 rockets. The bottom line is the United States can supply rockets at the rate of 400 per month indefinitely.

On the other hand, if usage rises to the Excalibur level of 1,000 a month, then inventories will decline gradually, hitting a critical state after about 20 months. That would be in early 2024. By that time, however, the production rate might be approaching the surge level, which could sustain that higher level of usage. However, high usage combined with a manufacturing lead time substantially longer than 17 months would create a period in 2024–2025 when usage would be capped, though at increasingly high levels, until manufacturing reached the surge rate.

Stinger. The United States last bought Stinger in 2004. (Actually, these were not new production missiles but upgrades of older missiles to Block I configuration.) Budget documents indicate that total production was about 2,900. The Army had planned to procure up to 11,000, but the end of the Cold War and the recognition that regional adversaries like North Korea had weak air forces drove large cuts to ground-based air defense systems.

The production line is apparently warm because of continuing foreign military sales. However, the number produced annually is likely small, in the vicinity of 100. When the United States bought Stingers, production reached about 350 a year, but that was 20 years ago. The U.S. Army has let a contract for additional Stingers and Congress has authorized more production, but it will take a long time to replace the lost inventory.

This may not be a problem, as the U.S. Army is developing several new air defense systems like M-SHORAD and the Indirect Fire Protection Capability. Because of these new systems about to enter the force, the United States may not need Stingers as urgently. Indeed, more Stingers might be sent to Ukraine with acceptable risk.

Causes for Optimism and Pessimism

Optimism – Most inventories are okay. These six systems do not represent the full spectrum of U.S. inventories. Most items provided to Ukraine have been in small numbers, or from areas that have large inventories or production capacities. For example, the United States has provided 108 million rounds of small arms ammunition, but U.S. production is about 8.6 billion rounds per year, so this transfer is easy to accommodate. The United States provided 300 M113 armored personnel carriers but has thousands available because the Army is moving to a different system. The United States has provided 276 tactical vehicles to tow weapons but has tens of thousands in inventory. For most categories of weapons and munitions, the United States can provide support indefinitely.

Pessimism – Not enough data to assess. Replacement times for several important systems cannot be calculated because not enough data is publicly available. For example, DOD cites sending Ukraine over 46,000 “other anti-armor systems” (not Javelin but types not specified), over 50 counter-artillery radars (various kinds), laser-guided rocket systems, unmanned aerial systems, and unmanned coastal defense vessels. It might be that some of these systems have inventory challenges, but the data are insufficient to make a judgment.

What Does the Future Hold?

As the September commentary noted, low inventories do not mean the end of equipment transfers. They do mean that the United States will need to pursue other mechanisms. DOD has, indeed, been pursuing all these but will need to intensify its work as the flow of aid becomes a multi-year operation.

Aid to Ukraine and rebuilding depleted inventories is one area when DOD cannot complain about congressional interference or sluggishness. Congress has provided ample funding in four supplementals, totaling $113 billion. Further, it has provided whatever authorities are needed, as seen in the recent National Defense Authorization Act (NDAA).

Substitutions. One mechanism for coping with low inventories is substitutions. Instead of Javelin, for example, the United States has been sending TOW anti-tank missiles. These are highly effective, though heavier and not portable by infantry. Although the TOW production rate has been low, about 1,000 per year, total inventories are high, with 176,000 built since the program's beginning decades ago.

Foreign purchases. The United States can buy equipment from foreign countries as it is doing with Czech T-72B tanks and South Korean 155 mm artillery projectiles. To do this, DOD has purchasing teams scouring the globe looking for weapons and munitions that might be suitable for transfer to Ukraine. The latest aid announcement shows the fruits of this effort: Soviet-standard 152 mm and 122 mm artillery shells and 125 mm tank shells purchased from third parties.

Accelerating procurement. Although procurement of new items will take many years, the process can go faster. One way is to waive certain provisions that are sensible in peacetime, when time is not a major factor, but are impediments when there is wartime urgency. The NDAA gave DOD authority to waive certain process requirements. DOD should take full advantage of those authorities.

Multiyear procurements. The NDAA gave DOD authority to sign multiyear procurement contracts for munitions. By making a multiyear commitment, DOD gives industry the incentive to invest money up front for a more efficient process. Industry has been worried that it will expand capacity but then, when the war ends, DOD will cancel its contracts, and industry will be stuck with excess capacity that many will regard as wasteful. DOD has used multiyear contracts for decades to buy ships, aircraft, and vehicles more efficiently. It should take advantage of these new authorities to rebuild its munitions inventories.

Accepting more risk. Finally, the United States could take additional risk by reducing inventories further. This would entail taking weapons from later-deploying reserve units and squeezing munitions inventory levels. These actions are uncomfortable, but, as Secretary Gates said in a different context, you focus on the war you have today, not the war you might have in the future. Indeed, elements in Congress are complaining that the military is keeping too much back over concerns about hypothetical future wars, particularly against a weakened Russia.

The bottom line is that military aid will continue, and Ukraine will still be able to resist, but inventory replenishment will become an increasingly pressing problem. DOD has many tools to mitigate the problem of “empty bins” and will need to use all of them to avoid a slackening of military support to Ukraine.

Mark F. Cancian is a senior adviser with the International Security Program at the Center for Strategic and International Studies in Washington, D.C.