What does ordnance require for it to unintentionally set off?

The correct answer highlights that outside intervention is a crucial factor that can lead to the unintentional detonation of ordnance. This refers to any external influence or action that can disturb the stability of the ordnance, such as physical interference, improper handling, combat damage, or other actions that compromise its integrity.

Understanding that unintentional detonation often stems from external factors is vital for safety protocols in handling ordnance. Ensuring that personnel avoid unnecessary contact and that ordnance is safely stored can mitigate the risks associated with outside intervention.

Other choices, while relevant to ordnance safety and functionality, do not specifically address the mechanism through which ordnance could unintentionally detonate. Internal mechanisms relate to how ordnance functions under normal conditions, environmental factors pertain to external conditions such as weather that might affect performance, and routine maintenance is important for ensuring ordnance is in working order but does not directly correlate with unintentional ignition caused by external actions.