TIL that after Spartacus was defeated, Crassus, the commander of the Roman forces, crucified 6,000 of the surviving rebels and lined the road with them—a crucifixion every ~100 feet for over 100 miles.
TIL during the chaos caused by the 1923 Great Kanto earthquake, the Imperial Japanese Army murdered an estimated 6,000 ethnic Koreans and Japanese socialists. The massacre is alternatively denied and celebrated by Japanese right-wing groups today.
TIL that despite underground room-and-pillar mining taking place as early as the 13th Century, the use of canaries for early warning of toxic gases began only in 1900, with mice first being used for the role in 1896.
TIL Paddy Chayefsky, author of cult film 'Network', was hugely successful in the 50s but by the 70s was out of work, forgotten, and suicidal. The legendary 'Mad as Hell' speech was his own personal thoughts, and reflected his own view of the world at that time.
TIL that for a time lots of navy ships and other military véhicule where painted in pink for better camouflage during dusk and dawn. The idea came from Lord Mountbatten after he saw a ship repainted in pink (the only colour available at the harbour) disappear in the sunset