The Darkest Hour presents the Imperial Japanese Navy offensive in the Indian Ocean area in March–April 1942, the main goal of which was to destroy the Royal Navy in the Far East and achieve domination on the western flank of the Pacific War on the eve of the Battle of Midway. The bold operation by two Japanese task forces (Kido Butai and Malay Force) in the Indian Ocean would only be possible with the fall of Singapore in February and the Dutch East Indies in early March 1942.

From the strategic point of view, the Japanese offensive in the Indian Ocean was the only moment in the Second World War when the Axis forces could coordinate their efforts to severely threaten the position of the British Empire in the crucial Middle Eastern and Indian theatres.

Volume 2 of The Darkest Hour describes the movements of the invincible Kido Butai, consisting of five aircraft carriers and their escorts, that expected to crush the British bases on Ceylon and once and forever destroy the main core of the Eastern Fleet. The chaos provoked by the Kido Butai would then become a great opportunity for the Malay Force to cut off the British shipping routes in the western part of the Bay of Bengal.

The Darkest Hour is the first systematic attempt to describe this less-well known part of the Pacific War by researching both British and Japanese archive documents and other sources published in many countries, including the United Kingdom, Japan, and India.

The second volume examines the Japanese aerial assault upon the British bases on Ceylon, and the attacks against the carrier HMS Hermes, cruisers MS Cornwall and Devonshire, and the destroyer HMAS Vampire. The Darkest Hour Volume 2 includes extensive tables detailing the composition of the Japanese air attacks and is illustrated with photographs and with colour artworks of the ships and aircraft involved.