Major wars depend on equipment held before fighting begins

A major power entering a war should expect to fight much of it with the equipment already available, because rebuilding stocks takes time. The war in Ukraine illustrates a different supply situation: major powers outside the fighting can transfer equipment from their own holdings. Keeping larger stocks provides more equipment to draw on, but maintenance and repair remain continuing expenses. Major powers also face the cost of keeping older equipment credible against a peer opponent. A cheaper second tier can still be called into that same war, exposing the assumptions behind maintaining it to a lower standard.