The whole house of Judah
does not refer to the entire population, man for man, but refers to those of the population who were building on the wall.
These builders represent the people as a whole inasmuch as the people had a mind to work,
but it was the builders who visibly expressed that mindset. As they laboured on the wall, these builders necessarily had their backs exposed to the enemies and the stones those enemies might throw. The leaders,
then, were eyes to them, ready to warn the labourers to drop their work and take up arms (Nehemiah 4:20).
16 From that day on, half of my servants worked on construction, and half held the spears, shields, bows, and coats of mail. And the leaders stood behind the whole house of Judah,