When are nuclear weapons moved by convoy according to transportation protocols?

The correct answer reflects the strict protocols surrounding the handling and transportation of nuclear weapons. According to these guidelines, moving nuclear weapons by convoy is mandated every time weapons are moved to ensure maximum security and safety. This process includes coordinated logistical measures to protect against threats and mishaps, reinforcing that nuclear weapons are treated with the utmost care at all times. This protocol is essential to safeguard not just the weapons, but also the personnel involved and the surrounding communities.

The other options suggest limitations or conditions under which convoys would be utilized. However, the comprehensive nature of the protocol emphasizes that every transport of nuclear materials is subject to the same rigorous security measures, regardless of the circumstances, thereby making the consistent use of convoys a fundamental requirement in the transportation process.