They Used Dark Forces

This novel concludes the stories of Obergruppenführer Grauber, Sallust's long term opponent, Graf von Ostenburg, the husband of Gregory's beloved Erica, and of his occasional lover Sabine.

While mainly concerned with the actual course of World War II and referring to many actual battles and moves of the years 1943–1945, embedded in the plot is an effective alternative history depicting how Nazi Germany could have won the war. It is set out in a very long monologue attributed to Hermann Göring (see Operation Felix). It assumes that in mid-1941 Goering convinces Hitler to drop the idea of invading the Soviet Union. Germany sticks to its 1939 non-aggression treaty with the Soviets, leaving Britain to go on fighting alone without allies. Instead, Germany directs its military might in the diametrically opposite direction. First, the German Army enters Spain, either getting Franco's consent or turning Spain into another Nazi-occupied country. Gibraltar is occupied and the Mediterranean closed to British shipping. Then the Germans move further southwards and in a swift move occupying the whole of Africa.

As noted by the book's Goering, the French colonies are controlled by the collaborator Vichy government which would impose no hindrance, Belgian and Portuguese forces in these countries' colonies are negligible and in the British colonies, military forces are designed to maintain colonial rule, not to resist an all-out German invasion. German forces would be able to swiftly reach South Africa, whose army would also be no match for the German army. South Africa would surrender after some bombing of Johannesburg and Pretoria, and part of the Afrikaner population would welcome German rule. With German fighter planes and U-boats based all along the West African coast, the Cape Route would be closed to British shipping. Britain would not be able to supply its forces in the Middle East, and would be largely cut off from India, Australia and New Zealand – which would be accessible only by the very long roundabout route across both the Atlantic and the Pacific – and there British shipping would run the gauntlet of Imperial Japanese naval and air power. Under such circumstances, Britain might be forced to end the war and recognize the fait accompli of German hegemony.