Defilade

Defilade – protection or shielding from hostile ground observation and flat projecting fire provided by an artificial or natural obstacle, as a hill [Dictionary.com].
Defilade – the arrangement of defensive fortifications to protect against enemy fire [Vocabulary.com].
– protection provided by obstacles against enemy crossfire from the rear, or observation.
– the disposition of defensive fortifications to produce this protection [The Free Dictionary].

Sources:

Defilade. The Free Dictionary. Retrieved from: https://www.thefreedictionary.com/defilade

Defilade. Vocabulary.com. Retrieved from: https://www.vocabulary.com/dictionary/defilade

Defilade. Dictionary.com. Retrieved from: https://www.dictionary.com/browse/defilade