What does the term “build-up” refer to in the context of munitions?

The term "build-up" specifically refers to the assembly of components into a complete explosive device. In the munitions context, this process is critical as it involves taking various parts—such as fuses, warheads, and propulsion systems—and combining them to create an operational munition. This assembly must be done with precision and adherence to safety protocols to ensure that the final product functions safely and effectively when deployed.

The other options describe related concepts but do not accurately capture the specific meaning of "build-up." The accumulation of used munitions pertains to disposal rather than assembly. The growth of a munitions stockpile involves inventory management rather than construction. An increase in personnel training focuses on education and skill enhancement, which is separate from the physical production or assembly of munitions. Thus, the choice that most accurately reflects the definition of "build-up" within the context of munitions is indeed the assembly of components into a complete explosive device.