Peter Jackson studied Cy Endfield's Zulu to understand how to shoot a fixed fortification under overwhelming assault — the claustrophobia, the hopelessness, the small group of defenders holding ground against infinite odds. Helm's Deep mirrors Zulu's architecture: a fort, an inferior force, a superior enemy, mathematical certainty of defeat holding against will and courage. Jackson cites this in the Appendices. Zulu is available on Criterion Channel.
Films That Influenced The Lord of the Rings: The Two Towers
