The twelfth book in the series was released in June 2017. The Alliance begins a more active fight against the League of Tripoli, a military coalition that was led by the Parti Populaire Français from a different alternative timeline in which France, instead of Germany, became the dominate fascist power in Europe. Some of the vessels that were brought over included the French submarine "Surcouf", the French Bretagne-class battleship "Savoie", the Italian Leone-class destroyer "Leopardo", and the Spanish Alsedo-class destroyer "Antúnez" along with a German Junkers Ju 52 trimotor transport aircraft and a squadron of Italian license-built Messerschmitt 109 fighter aircraft. The frequently mentioned mysterious German submarine was later revealed to be the Type XI U-boat U-112 in the next novel, "River of Bones".