Why Did Soldiers Fight In Lines?

Picked one by one from a mixed channel. Transcript check: both title readers certain; 5 of 5 sampled certain picks confirmed by transcript, none failed. Channel rule: Include only the long-form history and mythology documentaries that plainly teach a subject: national and civilizational histories such as 'History of Germany', 'The Minoans', 'Fall of the Spanish Empire', 'Full Story of Antarctica' and 'History of Halloween', plus scholarly mythology explainers such as 'Constellation Mythology Explained'. Exclude paranormal and creature episodes, listicles, trivia, speculative 'would see' pieces and sensational-hook titles.