We are not nocturnal in any way shape or form; our natural senses of sight, hearing and smell are just not up to the task which is why that out in the open at night we are easy prey.
However being human we fight our natural animal instincts and behaviour patterns and try to trick our bodies into thinking its still day with artificial light. While we can trick the eye we cannot fool the brain.
Science has shown us that the human body is at its lowest ebb at two in the morning. Combined this with our love of our weekends and you will find the time to plan a military attack against guarded defences is between two and three on a Sunday morning when the guards will be at their weakest and most vulnerable.