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Foot Archers and Infantry armed with rifles attack faster in melee.
—In-game description

Somali Jile Daggers is a technology in Age of Empires III: Definitive Edition - The African Royals that can be researched at a Trading Post built on a Somali settlement. Once researched, it reduces the rate of fire of foot archers and rifle infantry melee attacks by 35%.

Although not stated in-game, Somali Jile Daggers also increase the melee attack of Melee Skirmishers (e.g. Sudanese Dervish) by 20% and reduces the rate of fire of Urumis by 20%.