WASHINGTON — The Center for Strategic and International Studies reported that U.S. military contractors need at least three years to replenish stockpiles of Tomahawk, Patriot, and THAAD missile systems heavily used in the Iran war, creating a vulnerability window for a potential Western Pacific conflict. The U.S. fired over 1,000 Tomahawk missiles at Iran, and it could take until late 2030 to fully restore prewar inventory levels.

According to the CSIS report, the depleted inventories have created a window of vulnerability for a potential Western Pacific conflict. “The United States has enough munitions for any plausible scenario in the Iran war, but the depleted inventories have created a window of vulnerability for a potential Western Pacific conflict,” the report stated. It added, “The time needed to rebuild those inventories has thus become a major concern.”

The three systems serve distinct roles: Tomahawk cruise missiles strike targets deep inside enemy territory, while Patriot and THAAD interceptors defend against incoming missiles and drones. Replenishing more than 1,000 Patriot interceptors should wrap up in mid-2029, while replacing as many as 290 THAAD interceptors could take until the end of 2029. Fewer than 200 Tomahawk missiles are made per year due to historically small orders, though manufacturer Raytheon aims to increase production capacity to more than 1,000 annually.

“The problem today isn’t money; it’s time,” the report said. “It takes time to expand production capacity and to build these complex systems.” The window of vulnerability will last “for several years until inventories return to their previous levels and another several years before they get to the levels that war planners desire.”

Mark Cancian, a retired Marine colonel and senior adviser at CSIS who previously oversaw military hardware acquisitions at the Office of Management and Budget under Presidents George W. Bush and Barack Obama, traced the roots of the munitions shortfall to post–Cold War assumptions. After the Soviet Union’s collapse, the U.S. anticipated short, regional conflicts requiring few high-end weapons, leading to limited procurement and a small manufacturing base. “The thinking started to change, but it just takes time to build inventories,” Cancian said. He noted that Russia’s war with Ukraine demonstrated the need for deep munitions stockpiles in protracted conflicts.

Cancian credited the Biden administration with initiating industry discussions and investing in the defense industrial base, while acknowledging that “Now, it is true that the Trump administration really increased funding.” The report also noted logistical challenges, including complex supply chains and subcontractors producing specialized components. Deliveries of THAADs “were apparently re-sequenced to prioritize U.S. needs over those of allies and partners,” and “Patriot deliveries pose a dilemma for the United States because of the need to replenish its own inventories, help Ukraine defend against Russian missile attacks, and meet the needs of 17 other countries that use the interceptor.”