Over the past several quarters America has been running missile defense on three fronts at once: shielding Israel from ballistic missiles, shooting down Houthi drones and rockets over the Red Sea, and supplying interceptors to Ukraine. Wire reports state plainly that the missile stockpile is nearly exhausted, and while Washington denies it, the direction of travel is not in dispute: inventories of the most expensive interceptors (THAAD, Patriot, SM-3, SM-6) are now badly depleted and will have to be rebuilt.
The key observation, still underappreciated, is this: a defense budget can be raised in a matter of weeks, but an interceptor cannot be built any faster. The physical bottleneck in the entire chain is the solid rocket motor. Western production of these motors has shrunk to effectively two suppliers, and adding capacity takes years. That means restocking will stretch out over many years and will keep order books full far longer than any single escalation episode would suggest.