Napoleon managed to get by on as little as three hours sleep, especially during time of stress.
“Different subjects and different affairs are arranged in my head as in a cupboard. When I wish to interrupt one train of thought, I shut that drawer and open another. Do I wish to sleep, I simply close all the drawers and then I am – asleep, wrote Napoleon.”
According to supermemo, during sleep Napoleon was often interrupted by messengers, which perhaps lead to his napping at daylight. He commanded his subordinates to only be woken up with bad news, while the good news should wait.