“Day of the Zulu” seeks to explain why warriors armed with spears were able to wipe out 1300 British troops armed with state-of-the-art rifles in South Africa in 1879. The battle was “the worst defeat suffered by the British army during the Victorian era,” says historian Ian Knight (a descendant of a sergeant killed in it). Possible reasons: superior Zulu tactics, rifle jams, poor visibility (caused by gunsmoke and a solar eclipse) and Zulu “war medicines” (including cannabis and hallucinogens) that gave warriors a “very intense state of mind,” according to narrator Liev Schreiber.