Before fire man was of necessity a diurnal species. Wars were mainly fought in sunlight and in colder regions preferably in summer. Torches, candles and lanterns extended the options. After electrical light deviations multiplied in the human lifestyle on all fronts.
Vigilance in the dark was from earliest times necessary for keeping the species alive, and staying awake at times for reproducing it. Sunset is still the time for reflection, after hours of earning bread and baubles by the sweat of brows.
Unexpected flashes of recent troubles rise in recollection from a quietly spoken word, or spontaneously. An innocent external stimulus triggers traumatic memories of doings best forgotten. Even the last sunlight on some boulders reminds of where we come from.
The human preoccupation with war may be receding from minds preparing for millennia of peace, but the process is slow. Rocks like these posing sudden glimpses of exhausted horses and warriors catching their breath after losing their hope, remind of countercultures always present.