Why short-war assumptions hollow out the industrial base

Why do modern armed forces lack the infrastructure to replace equipment during a long war?

Decades of short-war assumptions allowed production capacity to disappear, forcing wartime procurement to recreate factories, tooling, and skilled workforces.

The short-war assumption grew from nuclear-era expectations that major conflict would rapidly destroy cities and end production planning. Afghanistan and other sustained operations exposed the weakness of that model. Without standing industrial capacity, urgent procurement must fund the design, factories, tooling, and a trained workforce before equipment can appear. Designing a replacement is only one part of rearmament when the physical production system has already disappeared.