Speculation
A siren woke up Nero long before sunrise, which was not a part of the plan though he was not surprised. As usual, he rushed from his bed towards his locker, with the only difference being that now the others in his bunker responded similarly.
When the siren rang there was no time for showers and they were supposed to report as soon as possible, so Nero was not surprised to see a number of lieutenants waiting for them as they lined up. All their luggage was already packed and loaded, so all that was left for them to do was get in the buses and roll out.
Even so, there was an element of haste in the air, as if even the superiors were in a rush to depart as soon as possible. Considering that the base was filled with the chaos that usually accompanied last minute changes that were made to plans, Nero didn't say anything and only silently observed.