The siege of Kimberley took place during the Second Boer War at Kimberley, Cape Colony, when Boer forces from the Orange Free State and the Transvaal besieged the diamond mining town. The Boers moved quickly to try to capture the area when war broke out between the British and the two Boer republics in October 1899. The town was ill-prepared, but the defenders organised an energetic and effective improvised defence that was able to prevent it from being taken.