This could possibly be their last night.
https://youtu.be/iRYvuS9OxdA
This is the third night of the assault (Sun, Mon, Tues).
Anyone who has been up for three nights in a row will be an incoherent shuffling zombie, or will just pass out no matter what is going on - combat ineffective.
Three nights of continuous bombardment is kind of a rule of thumb before sending your Infantry in, for that reason.