There are generally only three situations in which a group of zombies would leave a city.
"First, the order is given by the strongest zombie controlling the city. Second, a powerful enemy arrives in the city, forcing the zombies to flee in fear. Third, there is nothing left in the city and the zombies leave to find living humans for evolutionary purposes."
It's hard to determine which of the three situations are happening right now, so bases in various locations need to send out vanguards to investigate.
If it's the first or third possibility, it might not have anything to do with their safety as vanguards. But if it's the second possibility, then they might be in some bad luck.
Yin You also seemed to think so, looking somewhat worried.
