They actually have training / excercises within the Army (and I assume other branches), where they intentionally sleep deprive you while evaluating you on tasks. It’s assumed there will be points in battle where you can’t sleep. 24hrs without sleep happened fairly often, but the longest training that I can recall with sleep deprivation lasted 72 hours. Most people did manage to “sleep” during that time, but 20 minutes at most, as the cadence of the tasks was designed that you couldn’t sleep at all. I must admit though my platoon could mostly do our jobs in our sleep because the actions had been drilled into us and we had done them so many times with little or no sleep.